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DEPARTMENT  OP  THE  INTERIOR 
NITED  STATES  aEOLO( 


Bulletin  583 


COLORADO  FERBERITE  AND  THE 
WOLFRAMITE  SERIES 


BY 

FRANK  L.  HESS 

AND 

WALDEMAR  T,  SCHALLER 


^-:'v^-"">:-^  :"\ 


WASHINGTON 

UOY^RNMENT    PRINTING    OFFIC  J 

1911 


DEPARTMENT  OF  THE  INTERIOR 

UNITED  STATES  GEOLOGICAL  SURVEY 

GEORGE  OTIS  SMITH,  Director 


Buiii.ETiN'  683 


COLORADO  FERBERITE  AND  THE 
WOLFRAMITE  SERIES 


BY 

FRANK  L.  HESS 

AND 

WALDEMAR  T.  SCHALLER 


WASHINGTON 

GOVERNMENT    PRINTING    OFFICE 
1914 


F'^VV 


CONTENTS. 


Pagb. 

The  MINERAL  RELATIONS  OP  FERBERiTB,  by  Fraiik  L.  Hess 7 

Geography  and  production 7 

Characteristics  of  the  ferberite 8 

Geography  and  geology  of  the  Boulder  district 8 

Occurrence,  vein  systems,  and  relations 9 

Characteristics  of  the  ore 10 

Minerals  associated  with  the  ferberite 12 

Adularia 12 

Calcite 12 

Chalcedony , 12 

Chalcopyrite 12 

Galena 12 

Gold  and  silver 12 

Hamlinite  (?) 14 

Hematite  (specular) 15 

Limonite 16 

Magnetite 17 

Molybdenite 17 

Opal 17 

Pyrite 17 

Quartz 17 

Scheelite 17 

Sphalerite 17 

Sylvanite 17 

Spectroscopic  examination 18 

Crystallized  ferberite 19 

Composition  of  ferberite  and  other  members  of  the  wolframite  series 19 

Definition  of  ferberite  and  other  members  of  the  wolframite  series 37 

The  excessof  ferrous  oxide  and  manganous  oxide 38 

Crystallography  of  ferberite  from  Bouldei^  County,  Colo.,  by  Walde- 

mar  T.  Schaller 40 

Previous  publications 40 

General  characters  of  the  crystals 40 

Mode  of  occurrence 40 

Size 41 

Color  and  cleavage 42 

The  measured  crystals  by  localities 42 

Axial  elements 43 

Calculation  of  values 43 

Comparison  of  values 45 

Forms  and  angles ^ 

New  forms - ^"^ 

Forms  previously  described 52 

Common  forms ^ 

Bare  forms ^ 


• 


VMAJUM  ' 

4  CONTENTS. 

Page. 
Crystallography  op  perberite  from  Boulder  County,  Colo.— Continued. 

Discussion  of  the  prism  zone 55 

Habit 56 

Combinations 60 

Twinning 62 

Description  of  measured  crystals 65 

Form  system  of  the  wolframite  group 69 

Critical  study  of  forms 69 

Forms  and  coordinate  angles 71 

Combinations  observed  on  the  wolframite  group 73 

Bibliography 74 


ILLUSTRATIONS. 

Page. 
Plate  I.  Ay  Ferberite  inclosing  finely  brecciated  granite,  from  Rogers  tract, 
Nederland,    Colo.;  B,    ''Peanut  ore,"   ferberite  inclosing  finely 
brecciated  pegmatite,  from  the  Conger  mine,  Nederland,  Colo. ...        10 
II.  Brecciated  granite  and  pegmatite  cemented  by  ferberite,  from  Town 

Lot  mine,  Nederland,  Colo 11 

III.  Brecciated  ferberite  vein,  showing  crystals  formed  since  brecciation, 

from  Conger  mine,  Nederland,  Colo 12 

IV.  A,  Cut  and  polished  crystal  of  brown  ferberite  from  Winnebago 
claim,  near  RoUinsville,  Colo.;  B,  Brecciated  ferberite  vein  from 

the  Conger  mine,  Nederland,  Colo 13 

V.  Vug  in  a  ferberite  vein  nearly  filled  by  scheelite,  the  cavity  then 

remaining  being  filled  by  quartz 14 

VI.  A  and  B,  Thin  sections  of  ore  showing  hamlinite  (?),  from  Eagle 

Rock  mine,  8  miles  west  of  Boulder,  Colo 15 

VII.  A,  Wedge-shaped  ferberite  crystals  from  the  Lone  Tree  mine,  Neder- 
land, Colo.;  B,  Wedge-shaped  ferberite  crystals  from  the  Hoosier 

mine,  Nederland,  Colo 18 

VIII.  A,  Crystallized  ferberite  from  the  *'Crow  patent,"  Nederland,  Colo.; 
B,  Crystallized  ferberite  from  the  Georgia  A.  mine,  Nederland, 

Colo 19 

IX.  Crystallized  ferberite  with  elongated  rhombic  crystal  faces,  from  the 

Nugget  mine,  Gilpin  County,  Colo 20 

X.  Crystallized  ferberite  with  elongated  rhombic  crystal  faces,  from  the 

Nugget  mine,  Gilpin  County,  Colo. :  A,  Edge  view;  B,  Side  view..        21 
XI.  Ferberite  with  rhombic  crystal  faces,  from  the  Nugget  mine,  Gilpin 

County,  Colo 22 

XII.  Very  fine  specimen  of  ferberite  with  rhombic  crystal  faces,  from  the 

Nugget  mine,  Gilpin  County,  Colo 23 

XIII.  A,  Section  of  hiibnerite  from  the  Dragoon  Mountains,  Ariz.,  showing 

zonal  structures;  B,  Photomicrograph  of  granite  from  the  Whet- 
stone Mountains,  Ariz.,  showing  wolframite  with  warty  protuber- 
ances of  scheelite  along  its  edges 30 

XIV.  Section  of  wolframite  from  Irish  Creek,  Va.,  showing  interstitial 

scheelite 31 


ILLUSTRATIONS.  5 

Pace. 
Figure  1.  A,  Orthographic  projection  of  crystals  with  similar  combinations,  in 
parallel  grouping,  joined  by  the  g  (100)  faces;  B,  Same  with  dis- 
similar combinations 41 

2.  Superposed  crystals,  joined  by  the  q  (001)  faces 41 

3.  Long,  narrow,  wedge-shaped  crystal  of  habit  1 67 

4.  Short,  prismatic,  somewhat  flattened  crystal  of  habit  2 57 

5.  Tabular  crystal  of  habit  3 57 

6.  Cubic  crystal  of  habit  4 57 

7.  Rhombic  crystal  of  habit  5 67 

8.  Cleavage  pieces  of  crystals 58 

9.  Striations  on  wedge-shaped  crystals  of  habit  1 59 

10.  Crystal  No.  4,  wedge-shaped  habit 59 

11.  Peculiar  shape  of  wedge-shaped  habit  caused  by  cleavage 59 

12.  Crystal  of  short  prismatic,  somewhat  flattened  habit 59 

13.  Crystal  of  rhombic  habit,  nearly  equidimensional 59 

14.  Contact  twin  on  (023) 63 

15.  Contact  twin  on  (023) 63 

16.  Line  of  contact  of  two  contact  twins 63 

17.  Penetration  twin  on  (023) .' 64 

18.  Penetration  twin  on  (023) 64 

19.  Crystal  No.  29 64 

20.  Crystal  No.  32 64 

21.  Crystal  No.  33 64 

22.  Crystal  No.  5 66 

23.  Crystal  No.  6 66 

24.  Crystal  No.  9 66 

25.  Crystal  No.  13 66 

26.  Crystal  No.  16 67 

27.  Crystal  No.  17 67 

28.  CrystalNo.l8 67 

29.  Crystal  No.  19 67 

30.  Crystal  No.  20 68 

31 .  Crystal  No.  36 68 

32.  Cubic  crystal 68 

33.  Rhombic  crystal 68 

34.  Crystal  No.  26 68 

35.  Gnomonic  projection  of  forms  of  the  wolframite  group 70 


COLORADO  FERBERITE  AND  THE  WOLFRAMITE  SERIES. 


By  Frank  L.  Hess  and  Waldemar  T.  Schaller. 


THE  MINERAL  RELATIONS  OF  FERBERITE. 


By  Frank  L.  Hess. 


GEOGRAPHY  AND  PRODUCTION. 

Ferberite.  as  ordinarily  defined,  is  that  mineral  of  the  wolframite 
series  which  is  composed  wholly  or  almost  wholly  of  iron  tunssliatfi^ 
and  which,  like  other  wolframites,  crystallizes  in^the  monocUnic  sj[s^^ 
tem.  It  is  comparatively  rare  and  in  most  places  where  found  it  seems 
to  occur  in  small  quantities  only.  It  occuj.s.inJ,arggst, quantity  in 
Colorado^  about  25  miles  northwest  of  Denver,  mainly  in  Boulder 
County,  though  ItEe'  deposits  extend  a  short  distance  southward 
beyond  the  county  line  into  the  north  end  of  Gilpin  County.  From 
this  area,  which  has  a  southwest-northeast  length  of  about  12  miles 
and  a  width  of  6  to  7  miles,  an  equivalent  of  probably  7,300  short 
tons  of  concentrates  carrying  60  per  cent  WO3  had  been  mined  from 
1901,  when  exploitation  of  the  tungsten  veins  began,  to  the  close 
of  1912. 

The  relative  importance  of  the  Boulder  tungsten  field,  as  the  area 
is  generally  known,  is  indicated  by  the  statistics  of  the  production 
of  tungsten  ore  in  1910,  in  which  year  the  output  of  the  field  was 
1,221  tons.  In  the  same  year  the  output  of  Queensland  was  1,145 
tons;  Portugal,  1,132  tons;  Argentina,  1,061  tons;  and  the  world's 
production  was  probably  about  7,500  tons,  the  remainder  being 
smaller  lots  from  manj  countries.*  The  tungsten-bearing  mineral 
produced  from  the  three  countries  named  was  wolframite,  and  no 
other  country  produced  any  considerable  quantity  of  ferberite. 

» Fof  details  see  Hess,  F.  L.,  Tungsten:  U.  S.  Geol.  Survey  Mineral  Resources,  1910,  pt.  1,  p.  734,  1911. 
Since  the  above  paragraph  was  written  the  world's  statistics  for  1911  and  1912  have  become  available,  and 
these  show  that  Burma  has  outstripped  all  other  producers,  its  output  of  wolframite  being  equivalent  to 
2,095  short  tons  of  orecarrying  60  per  cent  W0|.    (Bee  U.  S.  Oeol.  Survey  Mineral  Resources,  1911  and  1912.) 

7 


8  COLOEADO  FERBERITE  AND  THE  WOLFRAMITE   SERIES. 

CHARACTERISTICS    OF    THE    FERBERITE. 

Ferberite  occurs  in  the  Boulder  County  field  not  only  in  large 
quantity,  but  in  places  in  clean,  beautifully  developed  crystals,  and 
very  commonly  in  small  crystals  coated  with  foreign  material. 
The  ferberite  found  over  most  of  the  field  is  jet  black,  but  in  a  few 
places  it  is  brown^  It  is  opaque  even  in  thin  sections  prepared  for 
microscopic  examination,  and  the  clean  crystals  and  cleavage  faces 
are  generally  lustrous  black. 

The  ferberite  of  Boulder  County  is  very  resistant  to  weathering 
and  forms  placers  which  have  been  successfully  worked.  The  fer- 
berite of  the  Black  Hills  (see  analysis  81,  pp.  32-33)  decays,  leaving 
a  skeleton  of  hydrous  iron  oxide,  and  wolframites  that  are  close  to 
ferberite  in  composition  decay  similarly,  but  no  alteration  has  been 
noted  in  the  ferberite  of  the  Boulder  field,  although  it  is  in  many 
places  coated  and  discolored  by  hydrous  iron  oxide  and  other  minerals. 

The  other  physical  characteristics  accord  fairly  well  with  those 
given  by  Dana  ^  for  the  wolframites.  The  cleavage  along  h  is  per- 
fect, and  in  some  specimens  a  parting  is  shown  parallel  to  a,  but  I 
have  not  noticed  the  parting  parallel  to  t  (102)  mentioned  by  Dana. 
The  fracture  is  uneven  and  the  mineral  is  brittle.  Its  streak  and 
powder  aie  dark  l)rown — nearly  black — an^^ts  Kardness  is  about^ 
Its  specific  ^avitv.  as  determined  on  selected  crystals,  is  7.499, 

^  A  splinter  of  pure  material  fuses  to  a  globule  which  has  a  crystalline 
surface  and  is  not  magnetic.  The  brown  mineral  from  the  Rogers 
tract  is  almost  infusible  before  the  blowpipe,  and  is  strongly  mag- 
netic after  heating. 

Although  ferberite  is  not  very  soluble  in  acids,  if  it  is  finely  pow- 
dered and  boiled  a  few  minutes  with  concentrated  hydrochloric  acid 
it  gives  a  solution  which,  on  the  addition  of  zinc,  readily  shows  a 
characteristic  blue  color,  followed  by  the  almost  equally  character- 
istic violet  and  brown. 

G«EOGRAPHY    AND    GEOLOGY    OF    THE    BOUIiDER 

DISTRICT. 

Nederland,  the  commercial  town  of  the  Boulder  tungsten  field, 
lies  2  miles  east  of  Cardinal  station,  on  the  Denver,  Boulder  &  West- 
ern Railroad,  and  4  miles  north  of  Rollins ville,  on  the  Denver, 
Northwestern  &  Pacific  Railway. 

The  ferberite-bearing  area  lies  on  an  elevated  plateau,  above 
which,  on  the  west,  rise  massive  and  imposing  peaks.  The  altitude 
at  Nederland  is  8,237  feet.  On  the  east  an  abrupt  scarp  descends 
from  the  plateau  to  the  Great  Plains.  Streams  draining  the  plateau 
have  cut  deep  canyons  extending  back  from  the  scarp  to  distances 
determined  by  the  abrading  power  of  the  streams. 

1  Dana,  E.  S.,  System  of  mineralogy,  6th  ed.,  p.  983, 1909. 


OCCURRENCE,  VEIN  SYSTEMS,  AND  RELATIONS.  9 

Biotite-homblende  granite,  in  some  places  gneissoid,  granitic 
crnflj^<;.  ancl  quartz-mjca  schist  form  the  country  rocks.  ^  The  gneiss 
wnH  ^^][yg|j  pe  older  thar^E^^ranite,  and  all  (lntc  arc  of  pre^am- 
brian  age  and  are  cut  by  later  dikes  that  raji<;(  in  composition  Irom 
Tlmburgite  to  granite  pegmatite. 

Dynamic  metamorphism  has  in  places  made  the  granite,  gneiss, 
and  schist  difficult  to  differentiate.  Some  of  the  dikes  are  also  more 
or  less  squeezed.  The  gneiss  is  believed  by  R.  D.  George  ^  and  Edson 
S.  Bastin^  to  be  of  sedimentary  origin.  The  pegmatites  show  only 
a  Uttle  crushing  and  carry  few  metallic  minerals. 

OCCURRENCE,  VEIN  SYSTEMS,  AND  RELATIONS. 

The  ferberite  occurs  in  a  grc^up  of  veins  whibh  in  general  extcndn^ 
from  southwost  to  northeast,  though  individual  veins  strike  toward 
"neai'ly  cvcmv  point  of  the  compass. 

On  \]\o  northwest  and  southwest  sides  of  the  tungsten-bearing  area  ^ 
are  gold  and  silver  bearing  veins  havuig  the  same  gene^*^|  ti^<^p^  »-^  ^^p 
tungsten  veins.     The  veins  carrying  the  precious  metals  are  acqntin- 
uation  of  the  gold-bearing  belt  of  Clear  Creek  and  Gilpin  counties.^ 

Two  types  of  veins  carry  the  gold  and  silver — those  in  which  the 
minerals  are  mostly  sulphides  and  those  in  which  the  gold  occurs  as  a 
fftHnrj^g^*  The  sulphidic  veins  are  in  general  quartz  veins  carrying 
gold\nd  silver  bearing  sulphides,  such  as  pyrite,  galena,  chalcopyrite, 
and  zinc  blende.  ..  Silver  predominates.  The  telluridic  veins  ^  occur 
in  sheeted  zones  and  contain  only  a  little  quartz.  They  carry  gold 
mostly  in  a  telluride,  which  is  probably  sylvanite,  and  the^^old  pre- 
dominates  over  the  silver.  Pyrite,  molybdenite,  a  vanadium  mineral 
allied  to  roscoelite,  barite,  "aHularia,  and  chalcedony  accompany  the 
telluride.     The  veins  are  thin  and  commonly  frozen  to  the  walls. 

JThe  ferberite  veins  are  more  or  less  connected  with  the  gold  veins, 
as  miglil  1)0  expected  from  the  general  grouping,  and  theu-  connection^ 
with  the  telluridic  veins  seems  closer  than  with  the  sulphidic  veins. 
Specimens  from  Magnolia,  at  the  southeastern  edge  of  the  field^ 
showed  both  gold  telluride  and  ferberite,  but  it  could  not  be  deter- 
mined which  was  the  older.  George  reports  a  like  specimen  in  which 
the  telluride  was  evidently  the  older  mineral."  He  also  reports  the 
occurrence  of  the  two  minerals  in  the  Wheelmen  Tunnel,  in  Boulder 
Canyon,**  and  at  Sunshine,  on  the  northern  -^dge  of  the  field.     A  speci- 

>  George,  R.  D.,  The  main  tungsten  area  of  Boulder  County,  Colo.:  Colorado  Geol.  Survey  First  Kept., 
pp.  19-20,  1909. 

«  Oral  statement. 

>  Lindgren,  Waldemar,  Some  gold  and  tungsten  deposits  of  Boulder  County,  Colo.:  Econ.  Geology,  voL 
2,  p.  453,  1907. 

*  Idem,  pp.  456-457. 
5  Idem,  pp.  457-459. 
« George,  R.  D.,  op. dt., p.  78.    ' 


10  COLORADO    FERBERITE   AND   THE    WOLFRAMITE    SERIES. 

men  from  Ward,  still  farther  north  and  beyond  the  territory  which  up 
to  this  time  has  been  productive,  shows  a  wolframite  which  is  prob- 
ably not  f  erberite  and  which  occurs  in  long,  slender  crystals  of  a  habit 
totally  different  from  that  of  the  f erberite  of  the  main  tungsten  area. 
Embedded  with  this  mineral  in  white  quartz  are  pyrite  and  chalcopy- 
rite,  apparently  of  the  same  general  age,  though  the  chalcopyrite  is  of 
later  deposition,  as  it  is  pierced  by  the  wolframite.  The  ore  is  said  to 
carry  both  gold  and  silver.  Although  the  data  at  hand  are  not  very 
extensive,  it  seems  probable  that  the  connection  between  the  three 
classes  of  veins  may  be  fairly  close  and  that  there  may  not  be  a  great 
difference  in  the  ages  of  the  several  types.  The  manganese  content  of 
the  tungsten  mineral  seems  to  increase  somewhat  progressively  across 
the  field  from  the  Gilpin  County  line  to  Ward — that  is,  from  south  to 
north.  A  few  miles  south  of  the  tungsten  field  in  Gilpin  County  pitch- 
blende has  been  found  in  considerable  quantity  in  close  connection  with 
gold  and  silver  bearing  veins,  which  lie  in  the  same  mineral  belt. 
Forbes  Rickard  has  recently  noted  ^  a  close  relationship  between  the 
ferberite  veins  of  Boulder  County  and  the  pitchblende  veins  of  Gilpin 
County. 

The  ferbgrite^X'gifis  much  resemble  those  carrying  gold  telluride. 
They  occur  in  sheeted  or  crushed  zones  and ^e  reticulated,  the  indi- 
vidual veins  ranging  from  a  small  fraction  of  an  inch  to  several  inches 
jn  thickness,^  while  the  ore-bearing  body  may  reach  a  width  of  14  feet, 
as  in  the  Philadelphia  mine  of  the  Wolf  Tongue  Mining  Co.  The  veins 
cut  granite,  gneiss,  and  pegmatite,  and  though  the  ore  may  extend 
from  the  granite  into  the  gneiss  it  may  be  cut  off  at  the  contact,  its 
continuity  depending  on  local  conditions,  but  there  are  only  a  few 
productive  veins  in  the  p;neiss»  "         -"-«*«- 

CHARACTERISTICS    OF    THE    ORE. 

The  amount  and  character  of  ganguc  in  the  veins  differ  greatly  in 
different  parts  of  the  field.  Quartz,  the  universal  vein  mineral,  occurs 
in  much  less  quantity  in  the  ferberite  veins  than  in  most  veins.  Only 
a  very  little  visibly  crystallized  quartz  in  the  ferberite  veins  lias  come 
to  my  attention.  There  is,  however,  in  most  if  not  in  all  of  the  veins  of 
the  northeastern  part  of  the  field,  and  in  many  of  the  wider  veins  of 
the  southwestern  part  of  the  field,  a  very  fine  grained  gray  or  brown 
_C[uartz,  known  as  ''bone,"  which  has  a  fracture  much  like  that  of 
chalcedony  and  which  is  largely  a  replacement  of  the  country  rock,  .^ 
The  ferberite  in  the  northeastern  half  of  the  field  appears  to  be  less 
well  crystallized  than  in  the  southwestern  half.  It  occurs  in  some  of 
the  veins  in  minute  particles  mixed  with  quartz  (see  PL  VI,  p.  15),  so 
lEat  in  many  places  the  ore  is  difficult  to  concentrate,  although  the 

1  Pitchblende  from  Quartz  Hfli,  Gilpin  County,  Colo.:  Min.  and  Soi.  Press,  June  7, 1913,  p.  852. 


U.    8.    GEOLOGICAL    SURVEY 


BULLETIN   SSI      PLATE   I 


A.     FERBERITE  INCLOSING  FINELY  BRECCIATED  GRANITE. 
From  Rogers  tract,  Nederland,  Colo.     Natural  size. 


B.     "PEANUT  ORE,"  FERBERITE  INCLOSING  FINELY  BRECCIATED  PEGMATITE. 
From  the  Conger  mine,  Nederland,  Colo.     Natural  size. 


#^^1" 


CHARACTERISTICS   OF   THE   ORE.  11 

total  percentage  of  WO3  may  be  as  high  as  or  higher  than  that  in  ores 
which  are  easily  and  profitably  worked. 

In  tho  s()nt]i\v(Nt(Mii  part  of  the  field  the  narrower  individual  veins 
aremado  up  alinost  wholly  of  ferberite,  wEich  has  ^own  from  both 
sides  of  th<^  ('.r('vi('.(^s  and  forms  conihs  of  small  (r\'stals  that  coalesce 
at  their  bases.  The  combs  are  of  fairly  uniform  thickness,  so  that 
although  in  the  narrower  crevices  they  may  have  met  and  grown 
together,  in  the  wider  cracks  they  form  bristUng  crusts  of  crystals  on 
each  side.  In  places  these  crystals  are  clean  and  bright  but  generally 
very  smaU,  from  one  to  three  thirty-seconds  of  an  inch  (1  to  2  milU- 
meters)  across.  Most  of  the  crystals  are  covered  with  a  coating  of 
impure  chaJcedony^jwhich  in  some  specimens  is  mixed  with  opal  and 
in  othei-s  contains  much  iron.  The  coating  generally  includes  small , 
crystals  of  ferberite,  which  are  of  course  of  a  latci-  generation  than 
those  on  the  walls.  Some  vugs  3  or  4  inches  across  are  entirely  filled 
with  such  a  mixture. 

On  the  Nugget  claim,  3i  miles  southeast  of  Nederland,  the  crusts  of 
nearly  pure  ferberite  reach  a  thickness  of  more  than  an  inch,  and  this 
claim  has  produced  the  finest  crystaUized  specimens  of  ferberite  yet 
found.  In  the  veins  of  this  claim,  as  in  the  others,  most  of  the  crys- 
talUne  aggregates  are  covered  with  a  sihceous  mixture,  which  here 
carries  much  brown  iron  oxide.  The  veins  cut  a  moderately  coarse 
grained  pegmatite  and  have  so  far  produced  only  a  small  quantity  of 
ore.  The  Winnebago,  an  adjoining  claim,  has  produced  some  small 
specimens  of  crystaUized  ferberite  from  similar  veins. 

In  places  the  country  rock  instead  of  being  sheeted  is  crushed  into 
smaller,  more  nearly  equidimensional  fragments,  which  may  not  be 
over  one-eighth  inch  (3  millimeters)  in  diameter.  Ore  in  which  frag- 
ments of  rock  no  larger  than  half  an  inch  (13  millimeters)  across 
are  embedded  in  ferberite  is  popularly  know^n  as  ''peanut"  or(\  from 
its  resemblance  to  peanut  candy.  (See  PL  I.)  Th<»  fiagnuMits  of  the 
breccia  vary  greatly  in  size  (PI.  II),  and  where  the  fragments  are  larger 
the  breccia  is  characterized  by  vugs  lined  with  ferberite  crystals. 
Both  finely  and  coarsely  brecciated  ore  is  typical  of  the  veins  of  the 
dis^rict^.  Many  of  the  veins  have  been  opened  several  times,  so  that 
the  ferberite  Itself  is  ])i(U',(',iated.     (See  Pis.  Ill  and  IV,  B.) 

In  places  i]w  fci  Ix^rlte  canlcs  considerable  manganese  and  grajd^ 
into  wolfi  aniitc.  The  mineral  from  Gordon  Gulch  carries  almost  6  per 
cent  MnO  (analysis  58,  pp.  30-31)  and  wolframite  occurs  on  the  norths 
_side  of  the  field  at  Ward  (analysis  49).  The  only  other  tungsten 
mineral  so  far  identified  in  the  field  is  scheelite.  which  occui-s  in  small 
quantity  as  a  thin  coating  of  octahedral  nearly  white  crystals  about 
one  thirty-second  inch  (1  miUimeter)  in  thickness,  over  a  film  of  fcy- 
j)erite  covering  the  walls  of  cre^'ices  in  the  Sugar  Loaf  district 
northern-central  part  of  the  area.     Vugs  in  ore  from  the  Frigid  Mining 


12  COLOKADO   FERBERITE   AND  THE   WOLFRAMITE   SERIES. 

Co.'s  claim  at  Crisman  are  lined  with  clear  brownish  and  colorl^ 
scheehte  crystals,  the  largest  three  thirty-seconds  of  an  inch  (2  milli- 
meters) ibluct.  Vugs  in  ore  from  the  Bogers  tract,  near  the  center  of 
the  area,  are  Hned  with  reddish-brown  scheelite,  which  also  occurs 
through  the  quartz  in  small  quantity.  Some  of  the  vugs  are  of  almost 
microscopic  size.  (See  PI.  V.)  As  seems  to  be  usual  in  tungsten 
deposits,  the  scheelite  formed  later  than  the  mineral  of  the  wolframite 
series,  but  it  is  not  a  secondary  mineral.     In  cleaning  certain  ferberfe 

i~  crystals  with  hydrofluoric  acid  deep  pits  with  rather  regular  outlines 
are  made,  accompanied  by  the  formation  of  yellow  tungsten  trioxide, 
and  it  seems  possible  that  the  pitting  may  be  due  to  the  removal  of 
scheehte. 

MINERAIiS    ASSOCIATED    WITH    THE    FERBERITE. 

Associated  minerals,  other  than  quartz,  are  few  and  scarce  in  the 
ferberite  veins  of  the  main  part  of  the  field.  Near  the  gold-silver 
bearing  areas  there  is  of  course  a  mixture  of  the  minerals  of  the  several 
vein  groups. 

The  following  minerals  accompany  ferberite  in  the  veins : 

Adularia. — Adularia  forms  a  coating  one-sixteenth  of  an  inch  (2 

millimeters)  thick  on  the  walls  of  the  Black  Hawk  No.  2  vein,  IJ 

[^{jfi^i       miles  south  of  Nederland.     It  is  beneath  most  of  the  ferberite,  but 

ijt^tfrf/  was  probably  deposited  with  the  first  of  the  ferberite.     Adularia  in 

microscopic  grains  is  found  in  many  of  the  veins. 

Calcite. — The  gangue  in  the  Conger  mine  carries  microscopic  parti- 
cles of  a  carbonate,  which  is  probably  calcite. 

Chalcedony. — Chalcedony  mixed  with  more  or  less  opal  and  hydrous 
iron  oxide  coats  crystals  from  many  of  the  veins. 

Q^olco^yrite. — Chalcopyrite  occurs  at  Ward  in  veins  carrying  some 
wolframite,  which  seems  to  approach  ferberite  in  composition,  though 
no  analysis  of  the  mineral  is  at  hand. 

Galena. — George  ^  reports  the  occurrence  of  galena  and  sphalerite 
in  veins  with  ferberite  near  Magnolia.  The  galena  is  said  to  occur 
generally  in  minute  cubes  but  in  considerable  quantity. 

Gold  and  silver. — Gold  and  silver  are  reported  to  occur  in  some  of 
the  ferberite  veins  other  than  those  in  which  sylvanite  is  present^ 
In  the  ore  seen  which  is  said  to  be  gold-bearing  smaU  quantities  of 
sulphides  are  present  and  the  ^old  is  probably  associated  with  the 
pyri|||^  Hills  2  states  that  eight  assays  of  concentrates  gave  an 
.    average  of  0.01  ounce  of  gold  to  the  ton. 

Greenawalt^  gives  three  analyses  of  concentrates  which  carried 
silver  in  quantities  of  1.2,  2.4,  and  3.1  ounces  to  the  ton.     The  speci- 

1  George,  R.  D.,  The  main  tungsten  area  of  Boulder  County,  Colo.:  Colorado  Geol.  Survey  First  Rept., 
p.  75, 1909. 

»  Hills,  V.  G.,  Tungsten  mining  and  milling:  Colorado  Sci.  Soc.  Proc.,  vol  9,  p.  150, 1909. 

•  Greenawalt,  W.  E.,  The  tungsten  deposits  of  Boulder  County,  Colo.:  Eng.  and  Min.  Jour.,  vol.  83,  p. 
951, 1907. 


.^    .^ 


CO  bs 
OC  c 
HI        o 


U.   S.   GEOLOGICAL  SURVEY 


BULLETIN  583      PLATE   IV 


A.     CUT  AND  POLISHED  CRYSTAL  OF  BROWN  FERBERITE. 

From  Winnebago  claim  near  Roll'msville,  Colo.     Shows  spongy  structure  of  theferberite,  the  pores  of  which 
are  filled  with  hydrous  iron  oxide.      X  78. 


B.     BRECCIATED  FERBERITE  VEIN. 


From  the  Conger  mine,  Nederland,  Colo.     Both  the   black  and  the  gray  edging  it  are  ferberite,  the  differ- 
ence in  color  being  due  to  the  orientation  of  the  crystals.     Natural  size. 


CHARACTERISTICS   OF   THE   ORE.  13 

mens  came  respectively  from  Beaver  Creek,  Nederland,  and  Gordon 
Gulch.  Tomblin  ^  states  that  m  the  Logan  mine  at  Crisman  free  gold 
is  sometimes  found  with  ferberite. 

The  occurrence  of  small  quantities  of  gold  and  silver  in  tungsten 
veins  is  fairly  common,  but  in  many  if  not  most  veins  the  precious 
metals,  though  of  the  same  general  period  of  vein,  f ormaiigya,  are 
nrobably  of  later  deposition  than  the  wolframite. 

Silver  seems  to  occur  in  greater  quantity  with  the  wolframites  thanj 
does  gold,  and  gold  in  greater  proportional  quantity  with  scheelite,! 
but  this  can  not  be  stated  as  an  invariable  rule. 

Hiibnerite  is  found  near  Pony,  Mont.,  in  quartz  veins  which  have 
been  worked  for  silver;  in  veins  prospected  for  silver  but  not  rich 
enough  to  work  near  Ellsworth,  Mammoth  district,  Nye  County, 
Nev.  (the  name  hiibnerite  was  given  by  Riotte  to  the  mineral  from 
this  place);  at  Butte,  Mont. ,2  on  the  300-foot  level  of  the  Gagnon 
mine,  where  hiibnerite " formed  an  oreshootof  argentiferous  material;" 
in  the  Birdie  mine  4  miles  east  of  Butte  (of  very  light  brownish-yellow 
color)  ;^  with  silver  minerals  in  the  Combination  mine,  Philipsburg, 
Mont.;*  in  the  mines  of  Silverton,  Colo.^  (wolframite  also);  and 
Tonopah,  Nev.®  Wolframite  occurs  with  silver  ore  in  the  Tip  Top 
mine.  Tip  Top  district,  near  Columbia,  Ariz.;  in  a  prospect  of  A.  C. 
Young's  at  Old  Hachita,  N.  Mex.;^  in  the  Victorio  district,  N.Mex.;* 
in  the  Sonoma  Range,  15  miles  south  of  Golconda,  Nev.;  at  Silver 
Mines,  10  miles  southeast  of  Ironton,  Mo.;'  and  on  the  Silver  Comet 
and  other  claims  southwest  of  Pioche,  Nev.  Wolframites  are  also 
found  with  deposits  carrying  more  gold  than  silver  in  the  South 
Homestake  mine,  White  Oaks,  N.Mex.;^^  gold  quartz  veins  on  Sheep 
Creek  near  Salmo,  British  Columbia; "  and  gold  mines  of  Lead,  S.  Dak. ; 
and  at  Cave  Creek,  Ariz.,  auriferous  pyrite  occurs  with  ferberite. 

1  Tomblin,  M.  B.,  Tungsten;  history,  occurrence,  uses:  Facts  concerning  tungsten  mining  in  world's 
greatest  Add,  Boulder  County,  Colo.:  Boulder  County  Metal  Mining  Association  Bull.  No.  3, 1912. 

2  Weed,  W.  H.,  Geology  and  ore  deposits  of  the  Butte  district,  Mont.:  U.  S.  Geol.  Survey  Pref.  Paper  74, 
p.  80, 1912.  See  also,  Pearce,  Richard,  The  association  of  minerals  in  the  Gagnon  vein,  Butte  City,  Mont. : 
Am,  Inst.  Min.  Eng.  Trans.,  vol.  16,  p.  64, 1888. 

»  Tomek,  F.,  Tungsten  in  Montana:  Min.  World,  vol.  28,  p.  68, 1908. 

*  Goodale,C.W.,and  Akers,  W.  A., Concentration  before  amalgamation  for  low-grade  partially  decomposed 
silver  ores,  with  notes  on  the  geology  of  the  Flint  Creek  mining  district:  Am.  Inst.  Min.  Eng.  Trans.,  vol. 
18,  p.  248, 1890. 

'Ransome,  F.  L.,Areportontheeoonomic  geology  of  theSilvertonquadrangle,  Colo.:  U.  S.  Gool.  Survey 
Bull.  182,  pp.  86-87,  256,  1901. 

•  Eakle,  A.  S.,  The  minerals  of  Tonopah,  Nev.:  California  Univ.  Dept.  Geology  Bull.,  vol.  7, 1912,  p.  18. 
Prof.  Eakle  calls  the  mineral  wolframite,  but  states  '-some  of  them  [the  crystals]  are  exceedingly  thin  and 
almost  transparent,  with  a  deep-red  color."  This  corresponds  with  a  specimen  in  my  possession  and  seems 
to  indicate  hiibnerite  rather  than  wolframite. 

T  Lindgren,  Waldemar,  and  others,  The  ore  deposits  of  New  Mexico:  U.  S.  Geol.  Survey  Piol.  Paper  68, 
p.  336,  1910. 

« Idem,  p.  292. 

•Haworth,  Erasmus,  A  contribution  to  the  Archean  geology  of  Missouri:  Am.  Geologist,  vol.  l,pp.  294- 
295, 1888. 

»o  Graton,  L.  C,  U.  S.  Geol.  Sursey  Prof.  Paper 68, p.  180, 1910.    See  analyses  4 and  16,  p.  24. 

"  Walker,  T.  L.,  The  occurrence  of  tungsten  ores  in  Canada:  Canadian  Min.  Inst.  Jour.,  vol.  11,  pp. 
867-371, 1908;  Reiwrt  on  the  tungsten  ores  of  Canada:  Canada  Dept.  Mines,  Mines  Branch,  p.  37, 1909. 


14  COLORADO   FERBERITE   AND  THE   WOLFRAMITE   SERIES. 

In  1907  a  lot  of  wolframite  ore,  weighing  1.1  long  tons,  from  Ravens- 
thorpe.  Western  Australia,  carried  66.2  per  cent  WO3  and  yielded  5.3 
ounces  of  gold.^ 

Examples  might  be  multiplied  but  would  add  little  weight.  The  im- 
portance of  those  given  lies  in  their  bearing  on  the  genesis  of  tungsten, 
gold,  and  silver  ores.  In  many  places  tungsten  ores  are  closely  con- 
nected  with  pegmatites  or  lie  in  the  pegmatites  themselves  and  are 
probably  in  nearly  all  places  close  to  a  magmatic  source.  The  gold 
and  silver  found  in  the  deposits  must  be  likewise  near  their  place  of 
origin.  Of  course,  it  is  not  to  be  argued  that  the  absence  of  tungsten 
mmerals  implies  that  the  gold  and  silver  may  not  be  near  a  magmatic 
source,  but  .goldjad-Sitefir  ^appear  to  accompany  sihceous  solutions 
much  farther  from  their  igneous  source  than  do  tungsten  minerals. 
It  seems  probable  that  the  tungsten  minerals  may  be  deposited  from 
the  hotter  waters  emanating  from  magmas,  and  silver  and  gold  from 
the  solutions  after  they  have  somewhat  cooled. 

Hamlinif.e  (jj. — In  sections  cut  for  microscopic  study  from  a  speci- 
men  obtained  at  the  Eagle  Rock  mine  many  small,  very  light  green 
fragments  of  a  uniaxial,  optically  positive  mineral  were  found.  As 
determined  by  E.  S.  Larsen,  its  indexes  of  refraction  are  6;=1.620± 
0.003,  £  =  1.630  ±0.003.  Its  birefringence  is  0.010,  but  some  basal 
sections  show  anomalous  birefringence  as  though  divided  into  seg- 
ments. It  has  a  perfect  basal  cleavage  and  shows  a  slight  zonal 
growth.  The  particles  show  a  tendency  toward  square  sections,  and 
the  optical  properties  suggest  that  the  mineral  belongs  to  the  alunite- 
hinsdalite  series.  Although  very  small,  the  particles  are  numerous, 
forming  perhaps  10  to  25  per  cent  of  the  bulk  of  this  particular  ore. 
(See  PI.  VI.)  The  gangue  is  ^'homy"  quartz  through  which  are  dis- 
tributed particles  of  ferberite  and  certain  other  particles  which  are 
attracted  by  a  magnet,  probably  magnetite,  both  of  which  occur  in 
grains  almost  as  small  as  the  unknown  mineral.  An  attempt  was  made 
to  separate  the  mineral  from  its  gangue  by  grinding  it  very  fine  and 
passing  the  powder  through  a  Thoulet  solution  of  2.8  specific  gravity, 
but  the  material  was  too  much  mixed  with  quartz  to  show  sufficient 
improvement  for  analytical  purposes.  The  fact  that  with  the  at- 
tached quartz  it  sank  through  the  liquid  indicates  that  its  specific 
gravity  is  above  2.8,  but  it  is  probably  not  over  3.  A  partial  analysis 
by  George  Steiger,  in  the  chemical  laboratory  of  the  United  States 
Geological  Survey,  showed  the  presence  of  aluminum,  2  per  cent 
strontium,  a  very  little  sulphur  as  a  sulphate,  and  3.6  per  cent  phos- 
phorus pentoxide.  The  only  heavy  metals  found  were  tungsten, 
iron,  manganese,  and  a  trace  of  titanium.  Fluorine  and  chlorine 
were  absent.  There  was  only  a  questionable  trace  of  calcium  and  a 
very  small  quantity  of  magnesium. 

1  Simpson,  E.  S.,  and  Gibson,  C.  G.,  The  distribution  and  occurrence  of  the  baser  metals  in  Western 
Australia:  Western  Australia  Geol.  Survey  Bull.  30,  pp.  115-117, 1907. 


I 


U.   S.   GEOLOGICAL  SURVEY 


BULLETIN    683       PLATE   VI 


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B. 

THIN  SECTIONS  OF  ORE  SHOWING  HAMLINITE. 

From   Eagle   Rock   Mine,   8  miles  vi/est  of  Boulder,  Colo.      Groundmass,  quartz.      Mineral  with   high   relief, 
hamlinite(?)     Black  mineral,  ferberite.      X  380. 


CHARACTERISTICS  OP   THE   ORE.  16 

The  mineral  seems  to  bo  close  to  hamlinite.  for  which  the  formula, 
as  recalculated  by  Ihw/'^is  2Sr().3.\l203.2P205.7H20,  but  as  a  little 
sulphur  is  present  it  probably  belongs  In  the  series  between  hamlinite 
and  svanbergite  (2SrO.3Al2O3.P2O5.2SO3.6H2O).  Another  mineral 
of  the  same  group,  hinsdahte  (2PbO.3Al2O3.P2O5.2SO3.6H2O),  was 
discovered  in  1010  by  Larsen  ^  as  a  vein  mineral  in  the  Golden  Fleece 
mine,  near  Lake  City,  Colo. 

The  same  mineral  has  been  found  in  sections  from  other  parts  of  the 
Boulder  field,  though  not  in  such  large  quantity  as  in  the  Eagle  Rock 
specimen.  Sections  of  '  'hornstone  "  ore  from  other  places  have  shown 
none  of  it.  Howevor.  pliosphorus  in  small  quantity  is  nearly  if  not 
quite  a  universal  conipuiieiit  of  the  Boulder  County  tungsten  ores,^ 

Hugh  F.  Watts,  who  has  assayed  thousands  of  samples  of  ferberite 
ores  and  concentrates  coming  from  all  parts  of  the  Boulder  field, 
states  that  whenever  he  has  tested  for  it  he  has  found  phosphorus 
present.^  In  one  test  on  a  composite  of  seven  ores  the  phosphorus 
present  amounted  to  0.038  per  cent.  Hills*  notes  from  0.01  to  0.02 
per  cent  phosphorus  in  eight  out  of  nine  analyses  of  concentrates 
and  a  trace  in  the  other.  Greenawalt  ^  notes  0.05  per  cent  in  a 
concentrate  from  Gordon  Gulch.  No  apatite  or  other  phosphate 
except  the  hamlinite  (?)  has  been  found,  and  it  seems  reasonable 
to  suppose  a  very  wide  distribution  of  the  hamlinite  (?).  The  min- 
eral apparently  occurs  only  in  the  quartz  gangue,  and  if  the  ore 
is  finely  ground  before  separation  very  little  will  be  left  in  the  con- 
centrates, for  its  specific  gravity  (more  than  2.8  and  probably  not 
higher  than  3)  is  so  low  that  it  would  readily  pass  into  the  tailings. 

I  hope  to  make  further  investigation  of  this  mineral. 

Hematite  (specular). — At  the  south  end  of  the  Black  Hawk  No.  1 
ve'in,  li  HUHS  y^UflTol  Nederland,  a  short  vein  which  is  nowhere  more 
than  a  few  inches  thick,  the  ferberite  gives  way  to  specular  hematite. 
This  mineral  is  also  found  in  small  quantity  in  soinc  other  veins,  and 
what  is  known  as  the  May  vein,  a  short  distance  east  of  the  Black 
Hawk  No.  1  vein,  is  a  series  of  anastomosing  veinlets  made  up  of  spec- 
ular hematite,  which  is  said  to  be  accompanied  by  a  Httle  tungsten, 
though  none  could  be  found  in  specimens  collected.  Hills  *  gives 
an  analysis  of  ferberite  concentrates  from  ''the  east  side  of  the  dis- 
trict,'^ in  which  the  content  of  FeO  exceeds  that  of  WO3,  and  another 
in  which  the  quantity  of  FeO  is  only  a  Httle  less  than  that  of  WO3. 
i'he  analyses  follow. 

1  Prior,  G.  T.,  Hamlinite,  plumbogummite  (hitchoockite),  beudantite,  and  svanbergite,  as  membenof 
a  natural  group  of  minerals:  Mineralog.  Mag.,  vol.  12,  p.  253, 1900. 

« Larsen,  E.  S.,  and  Schaller,  W.  T.,  Hinsdalite,  a  new  mineral:  Am.  Jour.  Sci,  4th  ser.,  vol.  32,  p.  251, 
1911. 

*  Private  communication. 

<  Hills,  v.  G.,  Tungsten  mining  and  milling:  Colorado  Sci.  Soc.  Proc.,  vol.  9,  p.  149, 1909. 

s  Greenawalt,  W.  E.,  The  tungsten  deposits  of  Boulder  County,  Colo.:  Eng.  and  Min.  Jour.,  vol.  83,  p.  951, 
1907., 


16  COLORADO   FEEBERITE   AND  THE   WOLFRAMITE   SERIES. 

Analyses  of  tungsten  concentrates  treated  at  the  Clarasdorf  mill,  near  Boulder,  Colo. 


Tungsten  oxide.. 

Iron  oxide 

Iron  sulphide 

Sulphur 

Manganese  oxide. 

Phosphorus 

Silicon  dioxide... 


38.46 

39.31 

.51 

.27 

3.10 

.01 

18.61 


34.01 

2.59 

1.38 

2.67 

.01 

22.13 


The  first  analysis  indicates  a  wolframite  of  the  composition  MnW04, 
26  per  cent;  FeWO^,  74  per  cent— a  composition  close  to  that  of  the 
Gordon  Gulch  wolframite  (analysis  No.  58,  p.  31).  After  satisfying 
the  MnO  present  only  8.8  of  the  39.31  per  cent  FeO  given  is  required 
to  combine  with  the  WO3.  The  second  analysis  indicates  a  wolfram- 
ite of  the  composition  MnW04,  22.7  per  cent;  FeWO^,  77.3  per  cent. 
This  composition  requires  for  combination  with  WO3  only  8.7  of  the 
34.01  per  cent  FeO.  The  form  in  which  the  iron  is  present  is  unknown, 
but  the  possibihty  that  it  maybe  specular  hematite  is  at  once  suggested 
by  knowledge  of  the  occurrences  mentioned.  The  sulphur  shown  in 
the  analyses  indicates,  of  course,  that  a  small  quantity  of  iron  is  pres- 
ent as  pyrite. 

Occurrences  of  specular  hematite  with  wolframites  are  not  un- 
known. At  South  Crofty  mine,  Cornwall,  ''the  presence  of  specular 
iron  has  caused  trouble  in  obtaining  a  high-class  wolfram  concen- 
trate.''^ 

It  seems  probable  that  deeper  workings  on  the  Rogers  tract  may 
show  specular  hematite,  to  the  decomposition  of  which  may  be  due 
the  brown  color  of  much  of  the  ferberite  from  that  tract. 

Limonite. — Limonite,  under  which  term  are  here  included  all  hy- 
drous  oxides  of  iron,  occurs  in,  many  veins^  and  nearly  all  the  ore 
on  the  Rogers  tract,  about  2  miles  northeast  of  Nederland,  is  stained 
brown  with  it.  The  crystals  of  ferberite  are  not  only  brown  on  the 
outside,  but  when  broken  show  brown  sections.  (See  p.  38  and  PI. 
IV,  A,  p.  13.)  The  origin  of  the  limonite  and  its  relationship  to  the 
ferberite  are  unknown,  but  in  part  at  least  it  is  possibly  altered  from 
specular  hematite,  as  already  stated.  Iron-bearing  carbonates  occur 
in  some  tungsten  deposits,  notably  the  scheelite  deposits  of  Atoha, 
Cal.  Carbonates  decompose  much  more  easily  than  specular  hema- 
tite, and  one  may  have  been  originally  inclosed  in  the  ferberite  of 
the  Rogers  tract  and  some  other  places. 

Magnetite. — Magnetite  is  recorded  by  George  ^  as  occurring  with 
the  ferberite.     Magnetite  seems  to  be  a  probable  associate  of  ferberite, 

1  Anon.,  Cornwall  (editorial):  Min.  Mag.,  London,  vol.  8,  p.  165, 1913. 

» George,  R.  D.,  The  main  tungsten  area  of  Boulder  County,  Colo.:  Colorado  Geol.  Survey  First  Kept., 
p.  75, 1909. 


I 


CHARACTERISTICS  OF  THE   ORE.  17 

but  in  several  specimens  of  powdered  ferberite  examined  I  have  not 
been  able  to  separate  it  with  a  horseshoe  magnet  nor  to  find  it  by 
microscopic  examination  with  reflected  light  in  polished  and  etched 
specimens  from  the  Western  Star  and  Nugget  claims.  In  the  ore 
from  the  Eagle  Rock  mine,  however,  a  small  quantity  of  magne^JQ^ 
material  which  is  probably  magnetite  was  ioun dT* 

Molvhdenite. — George*  and  Lindgren^  report,  though  Lindgren 
doubtfully,  that  molybdenite  occurs  with  the  ferberite  in  Boulder 
Coimty.  I  have  not  seen  this  association.  Molybdenite  is  a  com- 
mon  associate  of  wolfraniito  in  Queojislaiul  •'  and  is  also  found  witli  it 
in  Saxony  '^ncTlEngland,*  but  the  association  is  rare  in  this  country, 
though  molybdenite  occurs  with  wolframite  and  tourmahne  on  the 
Black  Horse  claims,  10  miles  southeast  of  Daisy,  Stevens  County, 
Wash.,  and  in  small  quantity  with  ferberite  at  Cave  Creek,  Ariz. 

Opal. — Opal  mixed  with  chalcedony  and  a  httle  hmonite  forms  a 
thin  opaque  yellowish-gray  coating  on  ferberite  crystals  in  the  Black 
Hawk  No.  1  vein,  IJ  miles  south  of  Nederiand,  and  is  probably  a 
constituent  of  the  sihceous  coating  on  the  ferberite  from  other  mines. 

Fyritc.  Pyrite  is  rare,  except  where  the  ferberite  veins  approacli 
the  gold  and  silver  veins,  though  here  and  there  a  little  may  be  found. 
^t  one  place  in  the  Conger  mine  a  vein  of  pyrite  2  inches  thick  cut 
across  the  ferberite  veins.  Iron  sulphide  in  quantities  reaching  3.25 
per  cent  ®  is  indicated  by  analyses  of  concentrates  from  a  number  of 
places,  as  noted  under  hematite. 

.Quartz. ^(^m\v\z  occurs  in  all  veins  in  comparatively  small  quantity.  ^ 
In  most  places  it  is  so  finely  granular  that  it  has  a  fracture  hke  chal- 
cedony,    Verv  httle  of  it  shows  crystal  form. 

ScheeMte. — For  discussion  of  the  occurrence  of  scheehte  see  pages 
11-12. 

SpJialerite. — Sphalerite  is  noted  by  George  (see  Galena,  p.  12),  and 
Moses  ^  states  that  he  found  small  yellow  crystals  upon  ferberite 
specimens  from  the  Boulder  field. 

Sylvanite. — As  has  been  noted,  sylvanite  occurs  with  ferberite  at 
Magnolia.     George®  also  notes  this  association  in  the  vem^'s^ose^T 
by  the  Wheelmen  Tunnel  in  the  lower  part  of  the  canyon  of  Boulder 
Oeek  and  in  a  mine  near  Sunshine. 

»  George,  R.  D.,  The  main  tungsten  area  of  Boulder  County,  Colo.:  Colorado  Geol.  Survey  First  Rept., 
p.  75,  1909. 
»  Econ.  Geology,  vol.  2,  p.  461, 1907. 

*  Cameron,  W.  E.,  Wdfram  and  molybdenite  mining  in  Queensland:  Queensland  Ged.  Survey  Rept. 
188, 13  pp.,  1904. 

*  Beck,  R.jUber  ein  kiirzlich  aufgeschlossenes  Wolframerzgangfeld  und  einige  andere  neue  Auiischliisae 
in  sachsischen  Wolframerzgruben:  Zeitachr.  prakt.  Geologle,  vol.  15,  pp.  38,40, 1907. 

«  Finlayson,  A.  M.,  The  ore-bearing  pegmatites  of  Carrock  Fell  and  the  genetic  significance  of  timgsten 
ores:  Geol.  Mag.,  vol.  7,  pp.  19-28, 1910. 

•  Hills,  V.  G.,  Tungsten  mining  and  milling:  Colwado  Sci.  Soc.  Proc.,  vd.  9,p.  149, 1909. 
T  Moses,  A.  J.,  The  crystallization  of  luzonite  and  other  crystall(^raphic  studies:  Am.  Jour.  Sci.,  4th  ser., 

vol.  20,  p.  282, 1905. 

•  Op.  cit.,  p.  76. 

35659°— Bull.  583—14 2 


18  COLORADO   FERBERITE   AND   THE   WOLFRAMITE   SERIES. 

SPECTROSCOPIC     EXAMINATION     OF     THE     FERBERITE. 

I     Scandium/   columbium,   tantalum,   and  other  rare  elements  are 
Ifoimd  in  some  wolframites,  and  a  specimen  of  ferberite  from  the  Con- 
'ger  mine  was  sent  with  a  specimen  of  scheehte  to  Prof.  G.  Eberhard, 
Potsdam,  Germany,  who  kindly  made  a  spectroscopic  analysis  of  them. 
In  a  letter  dated  August  20,  1912,  to  Adolph  Knopf,  of  the  United 
States  Geological  Survey,  Prof.  Eberhard  says: 
The  examination  of  the  two  minerals  from  Mr.  Hess  gave  the  following  results: 
The  lines  of  Ba,  Gl,  Pb,  Ga,  K,  Li,  Na,  Ni,  Ag,  Sn,  Bi,  Zn,  and  Zr  are  absent  in  both 
minerals.    The  lines  of  the  following  elements  are  present  in  ferberite: 
Al,  visible.  Mo,  weak?. 

Ca,  weak.  Sc,  weak. 

Cr,  weak  or  absent.  Si,  strong. 

Fe,  strong.  Sr,  weak. 

Cb,  weak.  Ti,  weak. 

Cu,  weak.  V,  weak. 

Mg,  visible.  W,  strong. 

Mn,  weak.  Y,  absent. 

I  have  not  sought  for  the  elements  not  here  listed.  Lines  marked  "weak  "  indicate 
that  the  content  of  the  element  is  small  or  very  small.  Lines  marked  "  visible ' '  indi- 
cate that  the  content  of  the  element  is  fairly  large.  Lines  marked  "strong "  indicate 
that  the  content  of  the  element  is  large.  The  element  whose  presence  I  could  not 
substantiate  with  absolute  certainty  I  have  marked  with  a  question.  The  content 
of  scandium  is  certainly  smaller  than  0.005  per  cent  and  is  therefore  chemically  not 
detectable. 

Since  this  determination  was  made  an  article  by  H.  S.  Lukens^ 

jhas  appeared,   in  which  he  describes  the  extraction  of  scandium 

[from  residues  of  Colorado  tungsten  ores  that  had  been  treated  by  the 

■General  Electric  Co.  at  Schenectady,  N.  Y.     Lukens  found  0.05  per 

cent  of  scandium  oxide  in  the  residues.     In  reply  to  my  inquiries 

the   Primos  Chemical   Co.,   which  had  furnished   the  ores,   wrote, 

under  date  of  April  18,  1914: 

-  Regarding  the  scandium  found  in  some  of  our  ores,  we  have  not  yet  located  the 
point  from  which  the  ores  come,  but  as  a  rule  our  residues  contain  no  scandium.  A 
great  many  tests  are  made  right  along.  As  we  are  getting  ores  from  a  great  many 
points  on  our  property,  it  is  very  difficult  to  tell  from  which  particular  openings  they 
came.  Most  Boulder  County  ores  contain  no  scandium.  Have  given  samples  right 
along  to  various  universities,  including  the  University  of  Pennsylvania,  and  though 
exhaustive  tests  have  been  made,  not  one  of  them  has  found  any  scandium. 

Another  letter,  dated  April  27,  1914,  says: 

As  far  as  our  records  show,  we  shipped,  with  the  probable  exception  of  one  small 
lot  from  Arizona,  only  Boulder  County  ores  to  the  General  Electric  Co. 

tNo  tungstic  ocher,  muscovite,  stibnite,  bismuth  minerals,  fluorite, 
tourmahne,  axinite,  cassiterite,  or  topaz — minerals  which  in  some 
places  occur  with  wolframite  deposits,  particularly  if  closely  connected 
with  pegmatites — are  known  to  have  been  found  in  the  Boulder  field. 

1  Winter  Herbert,  Ueber  Vorkommen  und  Reindarstellung  des  Scandiums:  Inaugural-Dissertation, 
Friedrich-Wilhelms-Universitat  zu  Berlin,  pp.  22-23  et  al.,  1911.  See  also  Mennicke,  Hans,  Die  Metallurgie 
des  Wolframs,  pp.  Ill  ct  seq.,  1911. 

»  Scandium  tn  American  wolframite:  Am.  Chem.  Soc.  Jour.,  vol.  35,  pp.  1470-1472, 1913. 


0.   8.   QEOLOOICAL   SURVEY 


BULLETIN   683      PLATE  VII 


A.     WEDGE-SHAPED  FERBERITE  CRYSTALS  FROM  THE  LONE  TREE  MINE,   NEDERLAND, 

COLO. 

Fan-shaped  intergrowth  m  right  center.     Coated  with  annmoniunn  chloride.      X  2. 


Ji.     WEDGE-SHAPED   FERBERITE  CRYSTALS  FROM  THE  HOOSIER   MINE,  NEDERLAND,  COLO. 
Fan-shaped  intergrowth  and  twins  in  lower  right  center.      Coated  with  ammoniunn  chloride.      X  2. 


U.    S.    GEOLOGICAL    SURVEY 


BULLETIN    583       PLATE   VIII 


A.     CRYSTALLIZED  FERBERITE  FROM  THE  "CROW  PATENT,"   NEDERLAND,   COLO. 

The  crystals  are  attached    by  the  C  axis  and   show   penetration  twins  and    reentrant  angles.     Coated  with 
ammonium  chloride.     Natural  size. 


1 

s 

wm^^mm^ 

4  ^^  '  * 

If 

w^'     AaT 

1"     '     ^v* 

.  ■■•1 

HPS^^^^^^^K   ^H 

V 

1^ 

I 

w^ 

IV    '•'V'-J'. 

i 

f  '■»--^  \ 

^^-    4 -=3^ 

1 

i?.     CRYSTALLIZED   FERBERITE  FROM  THE  GEORGIA  A.  MINE,   NEDERLAND,   COLO. 
Coated  with  ammonium  chloride.     X  10. 


COLORADO  FERBERITE  AND  THE   WOLFRAMITE   SERIES.  19 

CRYSTAIililZED    FERBERITE. 

As  has  been  stated,  the  ferberitc^  coninionly  ()cciij->  in  (Icfiniio 
crystal  forms  and  the  beauTyof  the  crystals  i>  imiquo.  However, 
although  crystals  are  common,  good  speciniciis  Miitable  for  display 
in  museums  are  very  rare,  for  most  of  the  crystals  are  so  small  that 
they  appear  insignificant;  they  are  very  fragile  and  are  easily  broken 
in  mininp:;  and  in  many  places  they  are  coated  with  mixtures  of 
cluilcodoiiy,  opal,  and  hychous  iron  ()xi(l(^s  in  varvin,i:  ])r()])()i-t ion^. 
This  coating  may  be  removed  from  some  specimens  without  serious 
injury  by  treatment  with  hydrofluoric  and  sulphuric  acids,  but 
crystals  so  treated  show  uneven  surfaces  when  an  attempt  is  made 
to  measure  them  with  a  goniometer. 

Probably  a  wedge  shape  is  the  commonest  form  of  the  crystals. 
This  form  occurs  in  many  of  the  mines.  One  of  the  best  specimens 
seen  is  from  the  Hoosier  mine,  between  1  and  2  miles  northeast  of 
Nederland  (PI.  YLl,  B) .  The  wedge  shapes  are  formed  by  the  termina- 
tions at  the  ends  of  the  h  axis  and  most  of  the  crystals  axe  attached 
at  one  end  of  this  axis.  Some  crystals  are  intergrown  in  such  a  way 
SiS  to  produce  a  fan  shape  (PL  \r[I,  A  and  B).  In  a  few  specimens 
crystals  attached  by  one  end  of  the  c  axis  are  prominent,  in  which 
case  the  termination  at  each  end  of  the  h  axis  is  shown.  Some  of  the 
crystals  show  penetration  twins,  extending  through  c{001}.  Around 
the  penetrating  crystal  in  two  or  three  occurrences  there  seem  to  be 
reentrant  angles  in  the  penetrated  members  (PI.  VIII,  A).  The  speci- 
men illustrated  came  from  a  tract  of  land  known  as  the  Crow  patent, 
near  Nederland. 

In  a  specimen  from  the  Greorgia  A.  claim  the  crystals  are  .almost 
cubic  and  about  one  one-hundredth  inch  (0.25  millimeter)  across. 
Plate  VIII,  Bj  represents  the  specimen  magnified  10  diameters. 

Another  form  of  crystal  is  found  on  the  Nugget  and  the  Winnebago 
claims,  near  RollinsviQe,  Gilpin  County.  In  this  form  the  crystal 
presents  a  face  (6)  which  is  a  long,  narrow  rhomb,  with  a  length  of 
about  three-eighths  inch  (9.4  millimeters)  and  a  width  one-tenth 
to  one-fifth  as  much.  Typical  specimens  are  shown  in  Plates  IX  and 
X.  In  some  specimens  the  rhomb  has  sides  much  more  nearly 
of  equal  length.  (See  PL  XI.)  Plate  XII  shows  a  very  fine  speci- 
men with  peculiar,  irregular  faces.  The  crystal  forms  are  described 
at  length  by  W.  T.  Schaller  in  the  latter  part  of  this  bulletin. 

COMPOSITION    OF    FERBERITE    AND    OTHER    MEMBERS 
OF    THE    WOLFRAMITE    SERIES. 

The^xiginal  f  erberite  was  found  in  the  Sierra  Almagrera,  in  southeru, 
Spain,  and  is  stated  by  Liebe  ^  to  have  been  named  by  Breithaupt 
for  K    Ferber,  of  Gera.     Liebe  made  an  analysis  of  the  mineral. 
(See^analysis  No.  79,  pp.  32-33.) 

1  Liebe,  K.L.H.,  Ein  neuer  Wolframite,  ein  Beitrag  zu  Mineral  Cbemie:  Neues  Jahrb.,  1S63,  pp.  540-563. 


20  COLOBADO   FERBERITE  AND  THE   WOLFRAMITE   SERIES. 

The  next  year  Rammelsberg  ^  published  an  article  on  ferberite 
with  an  analysis  of  his  own  material  (see  analysis  No.  82)  from  the 
same  locality  as  that  described  by  Liebe.  He  quotes  Liebe's  analysis 
and  shows  that  the  iron  oxide  and  tungsten  trioxide  are  not  in  a 
simple  ratio  and  that  there  is  an  excess  of  iron  oxide.  Neither 
mineral  was  pure,  and  the  analyses  are  not  very  satisfactory,  so 
that  calculation  of  iron  in  excess  is  uncertain,  for  it  was  probably 
present  as  an  impurity  and  not  as  a  part  of  the  mineral.  Liebe 
deducted  1.39  per  cent  limonite  from  his  analysis. 

It  seems  certain  that  the  calcium  present  should  be  calculated  as 
scheelite,  for  scheelite  almost  always  if  not  invariably  accompanies 
otBer^  tungsten  materials.  It  is  not  visible  in  all  specimens  to~tHe 
unaided  eye,  but  microscopic  examination  generally  shows  it  as  inter- 
stitial, inclosed  in  the  wolframite  crystals,  filling  vugs,  or  occurring 
separately  in  the  deposit.  (See  PL  V,  p.  14,  and  PI.  XIII,  A  and  B, 
p.  30.) 

Some  magnesium  was  found,  but  this  element  is  not  known  to  be  a 
constituent  of  tungsten  minerals,  although  A.  M.  Finlayson^  gives 
an  analysis  of  scheelite  from  Donaldsons,  New  Zealand,  containing 
0.2  per  cent  MgO,  which. he  considers  to  be  combined  with  WOg, 
taking  the  place  of  CaO,  and  Damour  ^  considered  that  both  calcium 
and  magnesium  might  take  the  place  of  iron  or  manganese  in  wolf- 
ramite. That  magnesium  takes  the  place  of  either  calcium  or  iron 
m  tungsten  minerals  seems  to  me  altogether  unlikely.  If  it  did 
so,  some  pure  tungsten  mineral — that  is,  some  mineral  which  could 
be  shown  by  microscopic  or  other  examination  not  to  contain  par- 
ticles of  other  substances — would  probably  be  found  in  which  the 
magnesium  would  form  a  considerable  part  of  the  mineral,  just  as 
do  those  elements  known  to  form  natural  tungstates — namely,  calcium, 
copper,  iron,  lead,  and  manganese.  Therefore,  in  recalculating  these 
and  other  analyses  on  pages  24-35,  neither  magnesium  nor  calcium 
has  been  considered  as  belonging  to  the  wolframite. 

To  obtain  a  basis  for  differentiating  ferberite  from  the  remainder 
of  the  woKramite  group  all  the  analyses  of  wolframites  (by  which 
term  is  meant  all  members  of  the  iron-manganese  tungstate  series) 
available  to  the  author  have  been  collected  for  comparison.  More 
than  300  analyses  were  examined,  but  of  these  some  represented  ores 
rather  than  minerals;  in  many  the  WO3  had  been  determined  by 
difference,  which  amounts  to  little  more  than  a  guess;  in  some  the 
figures  gave  evidence  that  either  the  analytical  work  was  bad  or  that 
the  material  was  so  impure  that  no  proper  comparison  of  the  results 
would  be  possible.  Where  several  analyses  of  the  same  material  were 
obtained,  only  one  has  been  tabulated. 

1  Rammelsberg,  C.  F.,  Uber  die  chemische  Zusammensetsung  des  Ferberite:  K.  Akad.  Wiss.  Berlin 
Monatsber.,  Jahre  1864,  pp.  175-176, 1865. 

2  FInlayson,  A.  M.,  The  scheelite  of  Otago:  New  Zealand  Inst.  Trans,  and  Proc,  vol.  40,  p.  112, 1908. 

3  Damour,  A.,  Sur  le  wolfram  tantalif6re  du  d^partement  de  la  Haute-Vienne:  Soc.  g6ol.  France  Bull., 
2d  sen,  vol.  5,  p.  108, 1848. 


U.   S.   QEOLOQICAL   SURVEY 


BULLETIN   683      PLATE  IX 


CRYSTALLIZED  FERBERITE  WITH  ELONGATED  R-^OMBC  CRYSTAL  FACES. 


From  the  Nugget  mine,  Gilpin  County,  Colo.     Coated  with  ammonium  chloride.     Natural  size. 


U.  8.   GEOLOGICAL  SURVEY 


BULLETIN    583      PLATE  X 


CRYSTALLIZED  FERBERITE  WITH    ELONGATED   RHOMBIC  CRYSTAL  FACES. 


From  the  Nugget  mine,  Gilpin  County,  Colo.     Coated  with  ammonium  chloride.     Natural  size. 
A,  Edge  view.     B,  Side  view. 


COMPOSITION  OF  FERBERITE  AND  OTHER  MEMBERS  OF  SERIES.       21 

The  analyses  have  all  been  recalculated  in  order  to  bring  them  to 
a  common  basis  on  which  they  can  properly  be  compared. 

To  do  this  it  has  been  assumed  that  the  theoretically  pure  members 
of  the  wolframite  series  contain  only  the  hiibnerite  molecule,  MnWO^; 
the  ferberite  molecule,  FeWO^;  or  a  combination  of  the  two  mole- 
cules.    All  analyses  have  been  reduced  to  these  simple  forms. 

As  scheeUte,  the  calcium  tungstate,.  CaWO^,  almost  universally  \ 
accompanies  the  wolframites,  the  lime  indicated  in  the  analyses  has 
been  considered  to  be  a  component  of  scheeUte  unless  data  given 
with  the  analysis  showed  it  to  belong  to  some  other  mineral,  such  as 
fluorite.  As  the  CaO  is  an  impurity,  it  has  therefore  ordinarily  been 
satisfied  with  WO3  and  then  discarded  with  all  items  other  than  FeO, 
MnO,  and  WO3.  Of  course,  this  scheme  probably  leads  to  error  in 
certain  of  the  analyses,  as  the  lime  in  some  may  be  derived  from 
other  sources  than  scheeKte,  but  these  sources  can  not  all  be  known, 
and  as  a  general  rule  the  process  just  described  seems  warranted. 
As  appli.ed  to  the  Boulder  field  in  particular  there  can  be  little  objec- 
tion^ as  lime-bearing  minerals  other  than  scheelite  are  unconmion, 
Calciferous  feldspars  seem  to  occur  in  very  few  places,  calcite  is  rare, 
and  no  other  lime  minerals  have  been  noted  in  the  veins. 

The  analyses  have  been  arranged  in  a  series  of  decreasing  MnWO^  j 
and  increasing  FeW04  content,  so  that  the  series  begins  with  the! 
hubnerites  and  ends  with  the  ferberites.  This  has  determined  the 
order  of  calculation,  for  the  natural  procedure  has  been  to  satisfy  first 
the  !MnO  with  WO 3  and  then  to  combine  the  remaining  WO3  with 
so  much  of  llie  FeO  as  it  would  take  up.  Arbitrary  or  casual  reasojpis 
are  not  the  only  bases  for  this  mode  of  calculation,  however,  for  man- 
ganese is  much  less  common  as  an  impurity  in  wolframites  than  is  iron. 
"  "The  quantity  of  MnWO^  and  FeWO^  obtained  as  a  result  of  the 
operations  has  then  been  treated  as  the  theoretically  pure  wolframite 
present  in  the  substance  analyzed,  all  other  substances  present  being 
considered  as  impurities.  From  the  theoretical  wolframite  as  a  basis 
have  been  computed  the  percentages  of  WO3,  FeO,  MnO,  FeWO^,  and 
MnW04  of  which  it  is  composed. 

In  making  the  calculations  the  following  atomic  values  and  molec- 
ular ratios  have  been  used : 

Atomic  weif ht. 

Calcium 40 

Iron 56 

Manganese 55 

Oxygen 16 

Tungsten 184 


Molecular  ratio. 


WO,      232  ^  ^^ 

WO,      232 

FeO  ~  72 

WO,  _  232 

MnO-TT ^'^^ 


3.22 


The  values  of  the  atomic  weights  are  used  only  to  the  nearest 
integer  and  the  ratios  to  the  second  decimal.    These  values  are  as 


22  COLORADO  FERBEEITE  AND  THE  WOLFRAMITE  SERIES. 

exact  as  are  warranted  by  the  errors  due  to  the  uncertainty  of  the 

constituent  minerals  of  the  analyzed  material  and  to  the  faults  of 

analysis. 

As  an  example  of  the  process  of  calculation,  analysis  37  may  be 

taken: 

Analysis  of  wolframite  from  Hill  City,  S.  Dak. 

Tungsten  trioxide  (WO3) 71.  0 

Ferrous  oxide  (FeO) 14.  3 

Manganous  oxide  (MnO) 10.  2 

Lime  (CaO) 0.  7 

Silica  (SiOz) 2.  9 

Magnesia  (MgO) None. 

Water  (H2O) 0.  3 

99.4 
WO3 
CaO  CaO  W0» 

0.7    X    4.14    =   2.9 

CaO  WO3  CaW04 

0.7+2.9      =3.6 
WO3 

MnO  MnO  WOi 

10.2    X    3.27    =  33.4 

MnO  WO3  MnWO* 

10.2    +   33.4    =   43.6 
WO3  required  to  satisfy  the  CaO  and  MnO 36.  3 


WO3  in  analysis 71.  0 

Less  quantity  for  CaO  and  MnO 36.  3 

WO3  to  be  satisfied  by  FeO 34.  7 


WOs 

WO3 

FeO  re- 
quired to 
satisfy  re- 
mainder of 
WO3. 

34.7 

4-   3.22 

=    10.8 

WO, 

FeO 

FeW04 

34.7 

+    10.8 

=   45.5 

FeO  in  analysis 14.  3 

FeO  required 10.  8 


Excess  of  FeO 3.5 

Adding  the  MnWO^  and  FeWO,, 

Hiibnerite  (MnWOJ 43.  6 

Ferberite  (FeW04) 45.  5 

Theoretical  wolframite  in  the  material  analyzed 89. 1 


U.    8.    QEOLOOICAL  SURVEY 


BULLETIN   883      PLATE   XI 


FERBERITE  WITH   RHOMBIC  CRYSTAL  FACES. 
From  the  Nugget  mine,  Gilpin  County,  Colo.     Coated  with  ammonium  chloride.     Natural  size. 


COMPOSITION   OF  FERBERITE  AND  OTHER  MEMBERS  OF  SERIES.       23 

Recalculating  to  percentages  of  the  theoretical  wolframite  and  then 
breaking  up  into  oxides, 

Hiibnerite  (MnWOJ 48. 9=11.  5  MnO+37. 4  WO, 

Ferberite  (FeWOJ 51. 1=12. 1  FeO +39. 0  WO, 

Total  WOs  in  theoretical  wolframite 76. 4 

The  presence  of  water  (0.3)  in  the  analysis  probably  indicates  that 
a  part  of  the  apparent  excess  of  FeO  (3.5)  is  limonite.  The  0.3  per 
cent  of  water  will  combine  with  1.6  per  cent  of  FeO  to  form  2.1  per 
cent  of  Umonite,  considered  as  2Fe303.3HjO.  Tliis  still  leaves  an 
excess  of  1.9  per  cent  FeO. 

Summarizing,  the  calculation  shows  the  wolframite  to  have  a  com- 
position of — 

W0» ^«-*l        'PeWO, 51.1 


76.41 

12.  ij  or  \i 

11.  sj       " 


Sio::::::::::::::::;""  --• "  ^**"^«' "" 

With  which  is  associated  in  the  mass  scheeUte,  CaWO^,  3.6;  excess 
FeO,  1.9;  Umonite,  2.1. 


24  COLOKADO   PERBEEITE   AND   THE   WOLFRAMITE   SERIES. 

Analyses  of  minerals  of 


Locality. 

Original  analysis. 

Mo. 

WO3. 

FeO. 

MnO. 

CaO. 

Si02. 

MgO. 

Other  sub- 
stances. 

Total 

1 

hObnerite. 
Philipsburg,  Mont 

74.82 
75.58 
74.28 
75.45 
74.88 
74.12 
70.21 
71.50 
74.32 
74.75 
75.12 
76.63 
75.94 
74.46 
75.36 
76.33 

76.50 
76.61 

0.06 

.24 

.47 

.55 

.56 

1.42 

2.03 

5.40 

2.11 

2.91 

3.01 

1.61 

2.38 

3.29 

2.66 

3.82 

4.40 
4.64 

25.00 
23.40 
22.73 
23.31 
23.87 
23.21 
21.72 
23.10 
20.90 
21.93 
20.54 
21.78 
21.57 
19.90 
19.50 
19.72 

18.50 
18.59 

99.88 
100.02 

99.69 
100.  51 

99.61 

? 

Ouray  County,  Colo.. 

0.13 
.02 
.32 
.14 

0.62 
1.33 

.48 

"b'.m 

None. 
.08 

61)266?,  0.05... 
M0O3,  trace... 
(CbTa)205?... 
CuO,0.08 

3 
4 

Emerald,  Nova  Scotia 

White  Oaks,  N.  Mex 

5 

Nye  County,  Nev. . 

fi 

Morococha,  Peru 

7 

Silverton,  Colo 

.37 

4.91 

Al2O3,0.56.... 

99.80 
100.00 
98.91 
99.70 
99.71 
100.11 
99.90 
99.87 

"io6."66' 

100.30 
100.21 

8 

Schlaggenwalde,  Bohemia 

Bayevka,  Russia 

q 

1.30 
.11 

1.04 
.09 

.28 

in 

North  Star  mine,  Colo 

Lawrence  County,  S.  Dak 

Cement  Creek,  Colo 

Trace. 

11 

1? 



Trace. 

13 

Patterson  Creek  Idaho 

Sunday  Gulch,  S.  Dak 

Dragoon  Mountains,  Ariz 

Bonito  Mountain,  N.  Mex 

Oroville,  "Wash 

S,  0  01 

14 
15 
16 

1.05 
'""."i3" 

.20 
.17 

.42 
1.70 

.70 

Trace. 

None. 
.20 

Ignition,  0.75.. 
Undet.,0.78... 

17 

18 

Bayevka,  Russia 

1.  Hubnerite  from  Philipsburg,  Mont.  Analysis  by  A.  H.  Low  quoted  from  Richard 
Pearce  by  Hillebrand,  W.  F.,  Miscellaneous  mineral  notes;  Contributions  to  the  min- 
eralogy of  the  Rocky  Mountains:  U.  S.  Geol.  Survey  Bull.  20,  p.  96,  1885. 

2.  Hubnerite  from  the  Royal  Albert  vein,  UncOmpahgre  district,  Ouray  County, 
Colo.  Hillebrand,  W.  F.,  Miscellaneous  mineral  notes;  Contributions  to  the  miner- 
alogy of  the  Rocky  Mountains:  U.  S.  Geol.  Survey  Bull.  20,  p.  96,  1885. 

3.  Hiibnerite  from  Emerald,  Nova  Scotia.  Johnston,  R.  A.  A.,  Hubnerite:  Can- 
ada Geol.  Survey  Ann.  Rept.,  new  ser.,  vol.  11,  p.  lOR,  1898. 

4.  Hubnerite  from  the  South  Homestake  mine.  White  Oaks,  N.  Mex.  Analysis 
by  J.  G.  Dinwiddie.  Besides  the  items  given  the  analysis  showed  HjO  at  110°  C, 
none;  H2O  above  110°  C,  0.40.  This  hubnerite  is  to  the  unaided  eye  as  black  as 
the  ferberite  of  the  Boulder  field,  but  in  thin  section  it  is  translucent  brown  and  olive- 
green.  The  streak  is  olive-green.  Microscopic  examination  showed  no  scheelite 
but  much  fluorite,  so  that  the  calcium  has  been  considered  as  derived  from  that 
mineral.    See  also  analysis  16. 

5.  Hubnerite  from  Riotte's  original  locality,  Ellsworth,  Mammoth  district,  Nye 
County,  Nev.  Genth,  F.  A.,  Contributions  to  mineralogy,  No.  52;  with  crystallo- 
graphic  notes  by  S.  L.  Penfield:  Am.  Jour.  Sci.,  3d  ser.,  vol.  43,  p.  187,  1892. 

6.  Hiibnerite  from  Morococha,  Peru.  Analysis  by  Pfiiicker  quoted  by  Domeyko, 
Ignacio,  Mineralojla,  vol.  2,  p.  92,  1897. 

7.  Hubnerite  from  the  Natalie  mine,  Silverton,  Colo.  Ekeley,  J.  B.,  Some  Colorado 
tungsten  ores:  Min.  World,  vol.  30,  p.  280,  1909. 

8.  Hiibnerite  from  Schlaggenwalde,  Bohemia.  Rammelsberg,  C.  F.,  Handbuch 
der  Mineralchemie,  p.  309, 1860.     Fine  red  brown  needles,  with  fluorspar  and  apatite. 

9.  Average  of  two  analyses  of  hubnerite  from  Bayevka,  Ural  Mountains,  Russia. 
Koulibin,  Von  N.  v.,  Manganhaltiger  Wolfram  aus  der  Grube  Bajewsk  am  Ural: 
Russ.-k.  mineral.  Gesell.  St.  Petersburg  Verb.,  vol.  3,  2d  ser.,  p.  3,  1868. 

10.  Hiibnerite  from  the  North  Star  mine,  Silverton,  Colo.  Genth,  F.  A.,  Contribu- 
tions to  mineralogy,  No.  52;  with  crystallographic  notes  by  S.  L.  Penfield:  Am.  Jour. 
Sci.,  3d  ser.,  vol.  43,  p.  186,  1892. 


COMPOSITION  OP  PERBERITE  AND  OTHER  MEMBERS  OF  SERIES.        25 
the  wolframite  aeries. 


No. 

Recalculated  analysis. 

Specific 
gravity. 

WOj. 

FeO. 

MnO. 

FeWOi. 

MnWOi. 

Excess 
FeO. 

Excess 
MnO. 

CaW04. 

1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 

17 
18 

76.6 
76.6 
76.6 
76.6 
76.6 
76.6 
76.6 
76.6 
76.6 
76.6 
76.6 
76.6 
76.6 
76.6 
76.5 
76.6 

76.6 
76.5 

23.4 
23.4 
23.4 
23.4 
23.4 
23.4 
23.4 
23.4 
23.2 
22.6 
22.0 
21.8 
21.8 
21.7 
20.7 
1&.9 

18.9 
18.8 

100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
99.2 
96.8 
94.0 
93.3 
93.1 
92.8 
88.4 
85.1 

80.9 
80.2 

0.1 

.2 

.5 

.6 

.6 

1.4 

2.0 

6.4 

1.9 

2.3 

1.2 

.1 

.8 

1.7 

.1 

.3 

2.1 
.5 

0.7 
.1 

7.177 

.2 

1.2 

.5 

.7 

1.2 

.7 

1.9 

6.45 

0.2 
.8 
1.4 
1.6 
1.6 
1.7 
2.8 
3.5 

4.5 
4.7 

0.8 
3.2 
6.0 
6.7 
6.9 
7.2 
11.6 
14.9 

19.1 
19.8 

6.7 
.6 

5.4 
.5 

7.357 

6.713 

6.891 

4.4 

4.1 

.7 

1.0 
1.0 

7.163 

Excess 
WO,. 

1.7 
.1 

7.20 

7.267 

11.  Hiibnerite  from  the  Comstock  mine,  Lawrence  County,  S.  Dak.  Headden, 
W.  P.,  Mineralogical  notes:  Colorado  Sci.  Soc.  Proc,  vol.  8,  p.  175,  1906.  "A  black 
mineral  fairly  well  crystallized." 

12.  Hubnerite  from  Cement  Creek,  Silverton,  Colo.  Genth,  F.  A.,  Contributions 
to  mineralogy,  No.  52;  with  crystallographic  notes  by  S.  L.  Penfield:  Am.  Jour.  Sci., 
3d  ser.,  vol.  43,  p.  186,  1892. 

13.  Hubnerite  from  the  Idaho  Tungsten  Co.'s  property  in  the  Blue  Wing  district, 
on  Patterson  Creek,  Lemhi  County,  Idaho.  An  unpublished  analysis  by  J.  E. 
Talmadge,  communicated  by  J.  G.  Lind.  It  seems  improbable  that  from  these 
deposits  a  specimen  could  be  selected,  the  analysis  of  which  would  show  neither  SiO^ 
nor  CaO,  but  this  is  of  course  surmise.  In  the  analysis  given,  were  the  ordinary  error 
of  high  MnO  made,  it  might  account  for  the  good  summation,  were  other  elements 
undetermined.  On  the  other  hand,  manganese  oxides  occur  in  the  vein  in  some 
quantity  (see  Umpleby,  J.  B.,  Geology  and  ore  deposits  of  Lemhi  County,  Idaho: 
U.  S.  Geol.  Survey  Bull.  528,  pp.  3,  etc.,  1913),  and  it  may  well  be  that  they  are  present 
in  interstices  of  the  hubnerite,  part  of  which  is  so  dark  as  to  suggest  the  inclusion  of 
either  manganese  or  iron  oxides. 

14.  Hubnerite  from  Sxmday  Gulch,  near  Hill  City,  S.  Dak.  Headden,  W.  P., 
Mineralogical  notes:  Colorado  Sci.  Soc.  Proc,  vol.  8,  p.  176, 1906.  "Granular,  almost 
entirely  free  from  admixed  gangue"  (p.  175). 

15.  Hubnerite  from  Dragoon  Mountains,  Ariz.  Guild,  F.  N.,  The  mineralogy  of 
Arizona,  p.  92,  1910. 

16.  Hubnerite  from  Bonito  Mountain,  near  White  Oaks,  N.  Mex.  Genth,  F.  A., 
Contributions  to  mineralogy,  No.  52;  with  crystallographic  notes  by  S.  L.  Penfield: 
Am.  Jour.  Sci.,  3d  ser.,  vol.  43,  p.  187,  1892. 

17.  Hubnerite  from  Oroville,  Wash.  R.  C.  Wells,  of  the  U.  S.  Geol.  Survey, 
analyst.  SiOj  includes  any  other  insolubles.  Ta,  Cb,  Sn,  Mo,  and  rare  earths  are  not 
present  in  appreciable  quantities. 

18.  Average  of  two  Mialyses  of  hubnerite  from  Bayevka,  Ural  Mountains.  Beck, 
W.,  and  Teich,  N.,  Ueber  Wolfram  und  Scheelit  aus  Fundorten  Russlands:  Russ.-k. 
mineral.  Gesell.  St.  Petersburg  Verb.,  2d  ser.,  vol.  4,  pp.  315-316,  1869. 


26  COLORADO   FERBERITE   AND   THE   WOLFRAMITE   SERIES. 

Analyses  of  minerals  of 


Locality. 

Original  analysis. 

Mo. 

WO3. 

FeO. 

MnO. 

CaO. 

SiOa. 

MgO. 

Other  sub- 
stances. 

Total. 

19 

WOLFBAMITE. 

Whetstone  Mountains,  Ariz.. 
Zinnwald,  Germany 

74.20 
76.20 
76.50 
73.60 
73.45 
75.62 
75.44 
76.01 
75.84 
75.68 
75.99 
76.34 

75.62 

72.80 
74.84 
74.90 
73.93 
7L90 
71.00 
74.86 

5.15 
5.60 
10.30 
11.20 
9.05 
9.55 
9.64 
9.81 
9.20 
9.56 
9.62 
9.61 

8.73 

11.44 
10.81 
10.60 
12.97 
15.29 
14.30 
13.45 

18.09 
17.94 
12.20 
15.75 
15.35 
14.85 
14.90 
13.90 
14.56 
14.30 
13.96 
14.21 

12.17 

12.08 
12.55 
12.80 
11.60 
10.64 
10.20 
11.02 

1.95 

99.89 
99.74 
100.10 
100.55 
100.00 
100.02 
99.98 
100.91 
99.60 
99.54 
100.05 
100.16 

}l00.99 

100.00 
100.38 
100.10 
99.53 

"'99.' 46" 
100.55 

90 

?1 

1.10 

Trace. 

81162,  trace... 

9,?. 

Zinnwald  (Germany?) 

LakeCouchiching,  Ontario... 
Zinnwald,  Germany 

23 
?4 

.20 

Cb205?,1.95... 

?5 

Altenberg,  Germany 

Tfi 

Zinnwald,  Germany 

1.19 

?7 

?8 

Schlaggenwalde,  Bohemia — 

Ziimwald  ( Germany?) 

Zinnwald,  Germany 

?9 

.48 

80 

31 

do 

Tenasserim,  Burma 

2.27 

1.18 
.80 
.30 

/Ti02l.89 

\H2O,0.31 

T^ss,0.14 

(Ta,C!b)  205,0.26 

PbO,  trace?... 

Ta2O6,1.03.... 

Undet.,  1.15.. 

H2O,0.30 

Cb203,  1.22.... 

3? 

2.36 
.30 
.■90 

■".■i2' 
Trace? 

S*^ 

Cornwall,  England. 

34 

Lost  River,  Alaska 

3'i 

Vilate,  France 

36 

Sudzukoya,  Japan 

'".'76' 

1.02 
2.90 

None. 

37 

Hill  City,  S.  Dak 

38 

Sierra  Cordoba,  Argentina... . 

19.  Wolframite  from  the  Whetstone  Mountains,  12  miles  south  of  Benson,  Ariz. 
Analysis  by  J.  M.  Ruthrauff  quoted  by  Guild,  F.  N.,  The  mineralogy  of  Arizona, 
p.  94,  1910. 

20.  Wolframite  from  Zinnwald,  Germany.  Bernoulli,  F.  A.,  Ueber  Wolfram  und 
einige  seiner  Verbindungen :  Poggendorf's  Annalen,  4th  ser.,  vol.  21,  p.  604,  1860. 

21.  Wolframite  from  Zinnwald,  Bohemia.  Helmhacker,  R.,  Wolfram  ore:  Eng. 
and  Min.  Jour.,  vol.  62,  p.  154,  1896. 

22.  Wolframite  from  Zinnwald  (Germany?).  Richardson,  T.,  Analysis  of  wolfram: 
Thomson's  Records  of  general  science,  vol.  1,  p.  451,  1835. 

23.  Wolframite  from  Lake  Couchiching,  Ontario.  Hunt,  T.  S . ,  Analysis  of  Canadian 
wolfram:  Canadian  Jour.,  new  ser.,  vol.  5,  p.  303,  1860. 

24.  Wolframite  from  Zinnwald,  Germany.  Kemdt,  T.,  Ueber  die  Krystallform  und 
chemische  Zusammensetzung  der  natiirlichen  und  kiinstlichen  Verbindungen  des 
Wolframmetalles:  Jour,  prakt.  Chemie,  vol.  42,  p.  97,  1847. 

25.  Wolframite  from  Altenberg,  Germany.  Kemdt,  T.,  Ueber  die  Krystallform 
und  chemische  Zusammensetzung  der  natiirlichen  und  kiinstlichen  Verbindungen 
des  Wolframmetalles:  Jour,  prakt.  Chemie,  vol.  42,  p.  110,  1847. 

26.  Wolframite  from  Zinnwald,  Germany.  Schneider,  R.,  Ueber  die  chemische 
Constitution  des  Wolframminerals:  Jour,  prakt.  Chemie,  vol.  49,  p.  332,  1850. 

27.  Wolframite  from  Neubeschert-Gliick,  Freiberg,  Germany.  Kemdt,  T.,  Ueber 
die  Krystallform  und  chemische  Zusammensetzung  der  natiirlichen  und  kiinstlichen 
Verbindungen  des  Wolframmetalles:  Jour,  prakt.  Chemie,  vol.  42,  p.  102,  1847. 

28.  Wolframite  from  Schlaggenwalde,  Bohemia.  Kemdt,  T.,  Ueber  die  Krystall- 
form und  chemische  Zusammensetzung  der  natiirlichen  und  kiinstlichen  Verbind- 
ungen des  Wolframmetalles:  Jour,  prakt.  Chemie,  vol.  42,  p.  109,  1847. 

29.  Wolframite  from  Zinnwald,  Germany  (?).  Ebelmen,  J.  J.,  Note  sur  la  com- 
position du  wolfram:  Annales  des  mines,  4th  ser.,  vol.  4,  p.  407, 1843. 

30.  Wolframite  from  Zinnwald,  Germany.  Kemdt,  T.,  Ueber  die  Krystallform 
und  chemische  Zusammensetzung  der  natiirlichen  und  kiinstlichen  Verbindungen 
des  Wolframmetalles:  Jour,  prakt.  Chemie,  vol.  42,  p.  96,  1847. 


COMPOSITION  OP  FERBERITE  AND  OTHER  MEMBERS  OF  SERIES.       27 

the  wolframite  series — Continued. 


No. 

Recalctilated  analysis. 

Specific 
gravity. 

WO». 

FeO. 

MnO. 

FeWO«. 

UnWO*. 

Excess 
FeO. 

Excess 
WO,. 

CaWO*. 

19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 

31 

32 
33 
34 
35 
36 
37 
38 

76.5 
76.6 
76.5 
76.5 
76.5 
76.5 
76.5 
76.5 
76.5 
76.5 
76.5 
76.5 

76.5 

76.5 
76.5 
76.4 
76.4 
76.4 
76.4 
76.4 

4.8 
5.4 
6.4 
7.1 
7.5 
8.5 
8.6 
8.7 
8.7 
9.1 
9.1 
9.3 
9.4 

9.9 
10.1 
10.3 
11.6 
12.1 
12.1 
12.3 

18.7 
18.0 
17.1 
16.4 
16.0 
15.0 
14.9 
14.8 
14.8 
14.4 
14.4 
14.2 

14.1 

13.6 
13.4 
13.3 
12.0 
11.5 
11.5 
11.3 

20.3 
23.0 
27.1 
30.1 
31.5 
35.8 
36.3 
36.6 
37.3 
38.3 
38.4 
39.2 

39.8 

41.9 
42.7 
43.3 
48.8 
50.9 
51.1 
61.9 

79.7 
77.0 
72.9 
69.9 
68.5 
64.2 
63.7 
63.4 
62.7 
61.7 
61.6 
60.8 

60.2 

58.1 
67.3 
56.7 
51.2 
49.1 
48.9 
48.1 

0.5 

.2 

4.6 

4.3 

1.9 

1.2 

1.2 

1.7 

.4 

.6 

.8 

.3 

.5 

2.6 
1.9 
.7 
1.8 
4.0 
1.9 
1.4 

6.7 

7.017 

7.230 

7.198 

6.1 

7.229 

7.535 



2.5 

11,7 

6.1 
4.1 
1.5 

7.272 

7.000 

(«) 

3.6 

a  Limonite  2.1  per  cent. 

31.  Wolframite  from  Zinn,wald,  Germany.  Weidinger,  G.,  Analyse  eines  Wol- 
framkrystalls  aus  den  Gruben  bei  sa-  hsisch  Zinnwald  an  der  bohmisch-sachsischen 
Grenze:  Zeitschr.  Pharm.,  vol.  7,  p.  73,  1855. 

32.  Wolframite  presumably  from  the  property  of  the  Mount  Pima  Mining  Co.  (Ltd.), 
Tenasserim,  Lower  Burma.  A  published  analysis  by  O.  Burger  furnished  through 
the  courtesy  of  Radcliff  &  Co.,  Rangoon,  Burma. 

33.  Wolframite  from  Cornwall,  England.  The  exact  locality  of  origin  is  unknown. 
Analysis  by  Edgar  T.  Wherry  on  specimen  No.  80179  in  the  United  States  National 
Museum.  The  analysis,  which  will  appear  in  the  Proceedings  of  the  Museum,  showed, 
besides  the  items  given:  FcaOg,  0.70,  which  was  calculated  to  its  equivalent  of  FeO 
and  added  to  that  item.  The  wolframite  is  black  and  opaque  and  occurs  in  large 
crystals  with  pyrite  and  chalcopyrite.  A  section  showed  a  later  deposition  of  very 
thin  bands  of  scheelite  and  wolframite  in  cracks  of  the  crystals,  so  that  the  CaO  evi- 
dently should  be  calculated  into  scheelite. 

34.  Wolframite  from  Lost  River,  Alaska.  R.  C.Wells,  of  the  U.  S.  Geol.  Survey, 
analyst.     No  Ta,  Cb,  Mo,  or  rare  earths  present. 

35.  Wolframite  from  between  Vilate  and  Chanteloube,  France.  Damour,  A.,  Sur 
le  wolfram  tantalif^re  du  d6partement  de  la  Haute-Vienne:  Soc.  g^l.  France  Bull., 
2d  ser.,  vol.  5,  p.  108,  1848. 

36.  Wolframite  from  Takatori  mine,  Takatori  Mountain,  near  Sudzukoya,  Higashi- 
Ibaraki  County,  State  of  Hitachi,  Japan.  The  mine  is  12  miles  northwest  of  Mito  and 
14  miles  northeast  of  Kasama.  Analysis  by  S.  Katsuno,  personal  communication, 
Nov.  30,  1912. 

37.  Wolframite  from  Black  Metal  claims,  Hill  City,  S.  Dak.  R.  C.  Wells,  of  the 
U.  S.  Geol.  Survey,  analyst.    Any  AI2O3  present  is  included  with  the  FeO. 

38.  Wolframite  from  the  southern  end  of  the  Sierra  Cordoba,  Argentina.  Boden- 
bender,  G.,  Die  Wolfram-Minen  der  Sierra  von  C6rdoba  in  der  Argentinischen  Re- 
publik:  Zeitschr.  prakt.  Geologie,  Nov.,  1894,  p.  409. 


28  COLORADO   FERBERITE   AND   THE   WOLFRAMITE   SERIES. 

Analyses  of  minerals  oj 


Locality. 

Original  analysis. 

Mo. 

WOa. 

FeO. 

MnO. 

CaO. 

SiOo. 

MgO. 

Other  sub- 
stances. 

Total. 

39 

WOLFRAMITE— continued. 
Lead,  S.  Dak 

61.70 
76.21 
70.38 
73.47 
74.78 
51.00 
64.13 
75.07 

74.43 

75.56 
71.27 
76.14 
73.46 
57.18 

9.18 
12.87 
13.88 
15.13 
13.80 
20.20 
10.88 
15.61 

16.90 

16.22 
20.01 
15.67 
16.90 
15.87 

8.21 
10.52 
9.52 
9.81 
9.36 
6.07 
6.42 
8.24 

8.37 

8.42 
7.15 
8.34 
6.97 
5.30 

0.93 

'"2."i6' 

.54 

Trace. 

"'i.'2i" 
.52 

12.87 
.15 

Trace. 

. 

99.64 
99.75 
100.  70 
100.05 
100.12 

40 

Montebelleux,  France 

Sadisdorf,  Germany 

41 

42 

do 

Tavoy,  Burma 

43 

.30 
L83 
7.71 

Trace. 

"i.'lh' 
.31 

Cb2O5,0.20.... 
As,  3.82 

44 

Wheal  Gorland,  Cornwall. .. . 
Northwest  Rpalri. . . . 

4,') 

SnO2,0.68 

Cb203,  1.12.... 

99.89 
100.87 

99.70 

100.20 
100.01 
100.15 
100.02 

46 

47 

Quebrada     de     la     Viuda, 

Argentina. 
Miramichi  River,  New 

Brunswick. 
Altai,  Siberia 

48 

49 

Ward,  Colo 

L68 

fiO 

Felsobany a,  Hungary 

Perilhao,  Portugal 

Wheal  Gorland,  Cornwall. . . . 

51 

2.69 
6.83 

52 

.  .               ... 
As,  2. 39 

39.  Wolframite  from  Two  Strike  mine,  Yellow  Creek,  Lead,  S.  Dak.  W.  F.  Hille- 
brand,  analyst.  Irving,  J.  D.,  Economic  resources  of  the  northern  Black  Hills:  U.  S. 
Geol.  Survey  Prof.  Paper  26,  p.  167,  1904.  Besides  the  items  noted,  the  analysis 
showed:  FegOg,  3.85;  AI2O3,  0.52;  SrO,  0.02;  BaO,  0.04;  KaO+NagO+LigO,  0.08; 
H2O,  below  105°  C,  0.20;  HgO  above  105°  C,  0.87;  AsgOg,  1.25;  P2O5,  0.12;  traces  of 
V2O5  and  S  or  SO3.  Extremely  minute  traces  of  Zn,  Cu,  Sb,  and  Sn  were  also  found. 
Assays  gave:  Gold  0.05  ounce  and  silver  0.25  ounce  to  the  ton  of  2,000  pounds.  The 
P2O5  was  probably  combined  with  CaO  as  apatite,  and  0.18  has  therefore  been  deducted 
from  the  CaO  before  combining  it  with  WO3  for  scheelite.  The  FeO  is  not  sufficient, 
as  indicated  by  the  analysis,  to  combine  with  the  WO3,  and  0.6  must  be  taken  from  the 
FejOg  to  supply  the  deficiency.  A  partial  analysis  of  a  specimen  from  the  Harrison 
mine,  near  Lead,  is  given,  as  follows:  SiOg,  9.60;  WO3,  61.70;  FcgOg  and  FeO,  12.67, 
MnO,  7.21;  CaO,  5.39.  Recalculated:  WO3,  76.5;  FeO,  9.5;  MnO,  14.0;  FeW04; 
40.2;  MnW04,  59.8;  CaW04,  39.4.  In  this  analysis  the  CaO  (5.39)  is  high,  and  no  de- 
termination of  P2O5  is  indicated.  There  is  no  corresponding  increase  in  the  WO3  and 
the  relation  of  the  FeO:  MnO  is  so  much  different  as  to  indicate  that  part  of  the  lime 
probably  belongs  in  apatite.  Specimens  of  ore  collected  by  the  present  writer  from 
this  general  locality  and  examined  microscopically  show  apatite  in  small  quantity. 
As  given,  the  analysis  falls  between  Nos.  31  and  32. 

40.  Wolframite  from  Montebelleux,  Brittany,  France.  Bourion,  F.,  Sur  un  mode 
general  de  preparation  des  chlorures  anhydres  et  ses  applications  h.  I'analyse  chimique: 
Annales  chim.  phys.,  8th  ser.,  vol.  21,  p.  103,  1910. 

41.  Wolframite  from  the  Kupfergrube,  Sadisdorf,  Germany.  Winter,  H.,  Ueber 
Vorkommen  und  Reindarstellung  des  Scandiums:  Inaugural-Dissertation,  Friedrich- 
Wilhelms-Universitat  zu  Berlin,  p.  23, 1911.  Besides  the  items  mentioned,  the  analy- 
sis shows  PO4,  2.23;  M0O3,  trace;  earth  acids  (TaOa,  TiOj),  2.07;  PbO,  0.46;  Sc,  0.2. 
It  is  stated  that  calcium  phosphate  was  present  in  the  gangue,  and  the  CaO  has  there- 
fore been  combined  with  the  PO4,  which  it  is  hardly  sufficient  to  satisfy. 

42.  Wolframite  from  the  Kupfergrube,  Sadisdorf,  Germany.  Winter,  H.,  Ueber 
Vorkommen  und  Reindarstellung  des  Scandiums:  Inaugural-Dissertation,  Friedrich- 
Wilhelms-Universitat  zu  Berlin,  p.  22,  1911.  The  analysis  also  showed:  Ti02  and 
TaOj,  0.63;  PbO  and  SnOg,  0.47;  Sc,  0.2. 

43.  Wolframite  from  the  Tavoy  district,  Lower  Burma.  Analysis  by  C.  S.  Fawcitt. 
Bleeck,  A.  W.  G.,  On  some  occurrences  of  wolframite  lodes  and  deposits  in  the  Tavoy 
District  of  Lower  Burma.    India  Geol.  Survey  Records,  vol.  43,  pt.  1,  pp.  67-68, 1913. 


COMPOSITION  OF  FERBERITE  AND  OTHER  MEMBERS  OF  SERIES.       29 

the  wolframite  series — Continued. 


No. 

Recalculated  analysis. 

SpecMo 
gravity. 

WO,. 

FeO. 

MnO. 

FeW04. 

MnW04. 

Excess 
FeO. 

Excess 
WO,. 

CaWO«. 

39 
40 
41 
42 
43 
44 
45 
46 

47 

48 
49 
50 
51 
52 

76.4 
76.4 
76.4 
76.4 
76.4 
76.4 
76.4 
76.4 

76.4 

76.4 
76.4 
76.4 
76.4 
76.4 

12.8 
13.0 
13.2 
13.4 
14.0 
14.5 
14.9 
15.0 

15.0 

15.1 
15.1 
15.2 
16.3 
16.6 

10.8 
10.6 
10.4 
10.2 
9.6 
9.1 
8.7 
8.6 

8.6 

8.5 
8.5 
8.4 
7.3 
7.0 

64.1 
64.8 
55.8 
56.4 
59.2 
61.0 
62.8 
63.2 

63.3 

63.6 
63.8 
64.3 
69.0 
70.0 

45.9 
45.2 
44.2 
43.6 
40.8 
39.0 
37.2 
36.8 

36.7 

36.4 
36.2 
35.7 
31.0 
30.0 

4.0 

0.2 

1.7 
3.0 
.1 
(?) 

2.8 

3.1 

6.2 
2.7 

1.3 

2.3 

1.3 
7.2 

.5 
1.2 

.2 

6.968 

8.1 

7.458 

Besides  the  items  noted  in  the  table,  the  analysis  shows  AljO,,  0.81;  BijOj,  0.14; 
SnOa,  trace;  M0O3,  0.51;  HjO,  0.22. 

44.  Ore  from  Wheal  Gorland,  Cornwall.  Analysis  by  B.  Kitto,  communicated  by 
Mr.  R.  Woodward,  managing  director  of  Edgar  Allen  &  Co.  (Ltd.),  Sheffield,  England. 
The  analysis  also  shows:  Pb,  0.10;  Mg,  trace;  Bi,  0.15;  P,  trace;  CaFj,  4.06;  Cu,  0.88; 
S,  2.02;  AI2O3, 1.77;  SnOj,  8.64;  O,  by  difference,  3.96.  Cu,  Fe,  S,  and  As  were  com- 
bined as  nearly  as  possible  to  form  chalcopyrite  and  arsenopyrite.  Although  not  made 
on  as  pure  material  as  might  be  wished  for  the  purposes  of  this  paper,  the  analysis  shows 
approximately  the  composition  of  the  wolframite. 

45.  Wolframite  from  northwest  Spain  (ore).  Steinhart,  O.  J.,  Classification,  occur- 
rence, identification,  and  properties  of  tungsten  ores:  Mineral  Industry,  vol.  17,  p.  830, 
1909.     The  analysis  also  shows:  AI2O3,  5.32;  and  CrO,  0.38. 

46.  Wolframite  from  Quebrada  de  la  Viuda,  Department  of  San  Xavier,  Argentina. 
Bodenbender,  G.,  Die  Wolfram-Minen  der  Sierra  von  C6rdoba  in  der  Argentinischen 
Republik:  Zeitschr.  prokt.  Geologie,  Nov.,  1894,  p.  409.  A  trace  of  CaO  is  pres- 
ent but  no  MgO. 

47.  Wolframite  from  the  confluence  of  the  southwest  Miramichi  and  Burnt  Hill 
Brook,  New  Brunswick.  Walker,  T.  L.,  Recently  discovered  wolframite  deposits  in 
New  Brunswick:  Econ.  Geology,  vol.  6,  p.  397,  1911. 

48.  Wolframite  from  Kolywanowschen  mine,  Altai,  Siberia.  Beck,  W.,  and  Teich, 
N.,  Ueber  Wolfram  und  Scheelit  aus  Fundorten  Russlands:  Russ.-k.  mineral.  Gesell. 
St.  Petersburg  Verb.,  2d  ser.,  vol.  4,  p.  317,  1869. 

49.  Wolframite  from  Ward,  Colo.  Analysis  by  J.  B.  Ekeley.  George,  R.  D.,  The 
main  tungsten  area  of  Boulder  County,  Colo.:  Colorado  Geol.  Survey  First  Rept., 
p.  43,  1909. 

50.  Wolframite  from  Felsobanya,  Hungary.  Sipocz,  L.,  Ueber  die  chemische 
Zusammensetzung  einiger  seltener  Minerale  aus  Ungam:  Min.  pet.  Mitt.,  new  ser., 
vol.  7,  p.  270,  1886. 

51.  Wolframite  from  Perilhao,  Portugal.  Bourion,  F.,  .Sur  un  mode  g^n^ral  de 
preparation  des  chlorures  anhydres  et  ses  applications  a  I'analyse  chimique:  Annales 
chim.  et  phys.,  8th  ser.,  vol.  21,  p.  104,  1910. 

52.  Ore  from  Wheal  Gorland,  Cornwall.  Analysis  by  B.  Kitto,  communicated  by 
Mr.  R.  Woodward,  managing  director  of  Edgar  Allen  &  Co.  (Ltd.),  Sheffield,  England. 
Fe  (12.34)  has  been  calculated  as  FeO  (15.87).  The  analysis  also  shows:  SnOj,  2.75; 
traces  of  Pb  and  MgO;  CaFj,  4.37;  Cu,  0.45;  S,  1.31;  AljO,,  4.13;  and  O,  by  differ- 
ence, 2.95. 


30  COLOEADO   FERBEKITE   AND  THE   WOLFRAMITE   SERIES. 

Analyses  of  minerals  of 


Locality. 

Original  analysis. 

No. 

WOj. 

FeO. 

MnO. 

CaO. 

SiOj. 

MgO. 

Other  sub- 
stances. 

Total. 

53 

WOLFRAMITE— continued. 
Meymac,  France 

74.75 

74.25 

76.00 
76.24 

71.2 

60.84 

75.79 
76.21 
70.73 
74.56 

76.57 
75.73 
75.82 
75.90 
76.02 

16.17 

15.85 

17.00 
16.39 

18.0 

18.36 

19.80 
18.54 
16.42 
15.19 

18.98 
18.68 
19.33 
19.25 
19.21 

6.40 

6.51 

6.60 
6.05 

6.0 

4.73 

5.35 
5.23 
4.71 
3.84 

4.90 
4.93 

4.84 
4.80 
4.75 

0.40 

.80 

.20 
1.05 

.32 

.40 

.50 

4.10 

.70 

1.12 

""."90' 

4.0 

16.28 

0.17 

.04 

None. 
.11 

TajO5,0.95.... 

fH2O,0.70 

\Ta2O5,1.10.... 

99.96 

}  99.25 

100.70 
99.84 

} 

} 

101.26 
100.74 
97.08 
100.20 

101. 15 
99.92 
99.99 
99.95 
99.98 

54 
55 

do 

Oreville,  S.  Dak... 

56 

Carrock  Fell,  England 

Mount  Carbine,  Queensland.. 

Gordon  Gulch,  Colo 

57 

/Bi,0.1 

\Cu,0.2 

fS,0.20... 

\P,0.05 

Sn02,  trace.... 

W 

Cabarrus  County,  N.  C 

Neudorf,  Germany 

60 

'".'26" 

'"".'se" 

.36 
.14 
.41 

Trace. 

61 

Pioche,  Nev  

(Ta,Cb)2O5,0.82 
(Ta,Cb)205,etc., 
0.96. 

6? 

Irish  Creek,  Va 

63 

Stassberg,  Germanv 

64 

Cedar  Canyon,  Wash 

Undet.,0.22... 

65 

66 

Harzgerode,  G  ermany 

Montevideo 

67 

53.  Wolframite  from  Meymac,  Correze,  France.  Camot,  A.,  Sur  quelques  min^- 
raux  de  tungst^ne  de  Meymac  (Correze):  Compt.  Rend.,  vol.  79,  p.  638,  1874.  Any 
alumina  present  is  included  with  the  silica. 

54.  Wolframite  from  Meymac,  Correze,  France.  Carnot,  A.,  Sur  quelques  min6- 
raux  de  tungst^ne  de  Meymac  (Correze):  Compt.  Rend.,  vol.  79,  p.  638,  1874. 

55.  Wolframite  from  "Wolfram"  claim,  3  miles  east  of  Oreville,  S.  Dak.  R.  C. 
Wells,  of  the  U.  S.  Geol.  Survey,  analyst.  SiOj  includes  any  other  insolubles.  Ta, 
Cb,  Sn,  Mo,  and  rare  earths  are  not  present  in  appreciable  quantities. 

56.  Wolframite  from  Carrock  Fell,  England.  Finlayson,  A.  M.,  The  ore-bearing 
pegmatites  of  Carrock  Fell  and  the  genetic  significance  of  tungsten  ores:  Geol.  Mag., 
vol.  7,  p.  21,  1910. 

57.  Wolframite.  Analysis  of  "typical  Mount  Carbine  [Queensland]  wolfram  con- 
centrate" by  Alex.  Cumming.  The  SiOg  (4.0)  includes  "insol.,  etc."  Besides  the 
items  in  the  table  there  is  also  "undetermined,  0.5."  Quoted  by  Ball,  L.  C,  Wol- 
fram mines  of  Mount  Carbine.  No.  1:  Queensland  Govt.  Min.  Jour.,  vol.  14,  p.  70, 
1913. 

58.  Ore  from  Gordon  Gulch,  Boulder  County,  Colo.  Greenawalt,  W.  E.,  The 
tungsten  deposits  of  Boulder  County,  Colo. :  Eng.  and  Min.  Jour.,  vol.  83,  p.  951, 1907. 
The  analysis  also  includes:  Gold,  trace;  silver,  3.1  ounces  to  the  ton.  The  item 
given  under  SiOa  is  given  by  Greenawalt  as  "Si." 

59.  Wolframite  from  the  Flowe  mine,  Cabarrus  County,  N.  C.  Genth,  F.  A.,  The 
minerals  of  North  Carolina:  U.  S.  Geol.  Survey  Bull.  74,  p.  80,  1891. 

60.  Wolframite  from  Grube  Pfaffenberg,  Neudorf,  Harz  Mountains,  Germany. 
Schneider,  R.,  Ueber  die  chemische  Constitution  des  Wolfram-Minerals:  Jour,  prakt. 
Chemie,  vol.  49,  p.  334,  1850. 

61.  Black  wolframite  from  Silver  Comet  mine,  11  miles  west  of  Pioche,  Nev.  J.  G. 
Dinwiddle,  analyst;  personal  communication.  The  analysis  also  showed  FejOg,  2.92; 
H3O  below  110°  C,  0.03;  HgO  above  110°  C,  0.57.    The  FeO  of  the  analysis  gave  an 


U.   8.  OEOLOOICAL   8URVEV 


BULLETIN   B8S      PLATE   Xni 


^ 


A.     HUBNERITE  from  the  dragoon  mountains,  ARIZ. 
Section  showing  zonal  structure.     X  5. 


B.     PHOTOMICROGRAPH  OF  GRANITE  FROM  WHETSTONE  MOUNTAINS,  ARIZ. 
Showing  wolframite  (black)  with  warty  protuberances  of  scheelite.     X  90. 


U,     S.    GEOLOGICAL    SURVEY 


BULLETIN    583       PLATE    XIV 


WOLFRAMITE  FROM   IRISH  CREEK,  VA. 
Section  showing  interstitial  sclieelite.     X  30. 


COMPOSITION  OF  FERBERITE  AND  OTHER  MEMBERS  OF  SERIES.       31 
the  wolframite  seriet — Continued. 


No. 

Recalculated  analysis. 

Specific 
gravity. 

WOs. 

FeO. 

MnO. 

FeWO<. 

MnWO«. 

Excess 
FeO. 

Excess 
WO,. 

CaWO«. 

53 

54 

55 
56 

57 

58 

59 
60 
61 
62 

63 
64 
65 
66 
67 

76.4 

76.4 

76.4 
76.4 

76.4 

76.4 

76.4 
76.4 
76.4 
76.3 

76.3 
76.3 
76.3 
76.3 
76.3 

16.6 

16.9 

16.9 
17.2 

17.2 

17.7 

18.1 
18.3 
18.3 
18.6 

18.6 
18.7 
18.8 
18.9 
18.9 

7.0 

6.7 

6.7 
6.4 

6.4 

5.9 

5.5 
5.3 
5.3 
5.1 

5.1 
5.0 
4.9 
4.8 
4.8 

70.1 

71.4 

71.4 
72.6 

72.5 

74.6 

76.6 
77.2 
77.4 
78.3 

78.3 
78.8 
79.2 
79.4 
79.6 

29.9 

28.6 

28.6 
27.5 

27.5 

25.4 

23.4 
22.8 
22.6 
21.7 

21.7 
21.2 
20.8 
20.6 
20.4 

0.4 

.1 

.4 
.2 

2.0 

4.3 

2.1 

.6 

2.8 

1.2 

1.1 
.2 
.7 
.5 
.4 

4.1 

2.1 

I.O 
5.4 

6.70 

1.7 
2.1 
3.3 
21.1 

3.6 

7.496 

7.  si 

7.228 

7.513 

excess  of  0.2  and  to  this  has  been  added  2.6,  the  equivalent  of  the  FejOj  given.  In 
appearance  the  material  is  so  pure  that  it  is  difficult  to  account  for  the  apparent 
presence  of  3.3  per  cent  of  scheelite  (CaW04).  Possibly  the  "H2O  above  110°  C, 
0.57,"  should  be  CO2. 

62.  Wolframite  from  Cash  tin  mine,  Irish  Creek,  Rockbridge  County,  Va.  Analysis 
by  J.  G.  Dinwiddie.  The  analysis  also  shows  FeaOg,  4.03;  FeO,  11.56;  HjO 
at  110°,  0.12;  H2O  above  110°,  0.63;  TiOg,  0.02;  AlA*  0.32;  CO2,  0.5.  The 
FejOg  has  been  changed  to  FeO  and  added  to  that  item.  It  is  extremely  difficult  to 
make  accurate  determinations  of  ferric  and  ferrous  iron  in  the  wolframites,  owing  to 
the  likelihood  of  part  of  the  iron  being  oxidized  during  grinding  and  difficulties 
inherent  in  the  chemical  determination.  The  change  also  makes  the  analysis  foot 
up  better.  The  scheelite  (CaW04)  is  very  high,  (21.1),  but  specimens  of  wolframite 
from  the  locality  show  many  inclusions  of  scheelite.     (See  PI.  XIV.) 

63.  Wolframite  from  Neuhaus  Stollberg,  Stassberg,  Harz  Mountains,  Germany. 
Analysis  by  Petzold.  Schneider,  R.,  Ueber  einen  harzer  Wolfram:  Poggendorf's 
Annalen,  4th  ser.,  vol.  3,  p.  474,  1854. 

64.  Wolframite  from  the  Germania  mine.  Cedar  Canyon,  Stevens  County,  Wash. 
R.  C.  Wells,  of  the  U.  S.  Geol.  Survey,  analyst. 

65.  Wolframite  from  Chanteloube,  Limoges,  France.  Kemdt,  T.,  Ueber  die  Krys- 
tallform  und  chemische  Zusammensetzung  der  natiirlichen  undkunstlichen  Verbind- 
ungendes  Wolf rammetalles :  Jour,  prakt.  Chemie,  vol.  42,  p.  105,  1847. 

66.  Wolframite  from  Harzgerode,  Germany.  Kemdt,  T.,  Ueber  die  Krystallform 
und  chemische  Zusammensetzung  der  natiirlichen  und  kiinstlichen  Verbindungen 
desWolframmetalles:  Jour,  prakt.  Chemie,  vol.  42,  p.  105,  1847. 

67.  Wolframite  from  "Monte  Video,"  country  not  given,  Kemdt,  T.,  Ueber  die 
Krystallform  und  chemische  Zusammensetzung  der  natiirlichen  und  kiinstlichen 
Verbindungen  des  Wolf  rammetalles:  Jour,  prakt.  Chemie,  vol.  42,  p.  102,  1847. 


32  COLORADO  FERBEKITE  AND  THE  WOLFRAMITE  SERIES. 

Analyses  of  minerals  of 


No. 


Locality. 


Original  analysis. 


WO3. 


FeO. 


MnO. 


CaO. 


SiOo 


MgO. 


Other  sub- 
stances. 


Total. 


FERBERITE. 


Limoges,  France 

Traversella,  Italy 

Nagpur,  India 

Estremadura,  Spain 

Inverell.  New  South  Wales 

Neudon ,  Germany 

Torrington,  New  South  Wales 

Gordon  Gulch,  Colo 

Neudorf,  Germany 

Beaver  Creek,  Colo 


Cave  Creek,  Ariz 

Sierra  Almagrera,  Spain 

Kootenay  Belle  mine,  British 
Columbia. 

HUl  City,  S.  Dak 

Sierra  Almagrera,  Spain 

Adun-Tschilon,  Siberia 

Ivigtut,  Greenland 

Last  Chance,  Colo 


76.20 
75.99 
61.59 
72.93 
77.64 
76.30 
70.73 
61.80 
76.28 

66.41 
73.74 
70.11 
74.90 

70.94 
69.06 
75.55 
75.19 
62.30 


19.19 
16.29 
14.50 
22.70 
18.76 
20.12 
18.13 
16.36 
20.38 

24.31 

18.18 
23.29 
17.75 

17.61 
25.97 
21.31 
22.97 
19.90 


4.48 
3.45 
2.94 
4.10 
4.12 
4.12 
3.64 
3.12 
3.80 

3.25 

3.37 
3.02 
2.75 

2.71 
2.17 
2.37 
L33 


0.80 


3.40 


P,  0.018. 


.38 

L64 

.35 

.20 


15.93 


.16 

Trace. 

1.71 

.07 


Gangue,  6.55., 
AljOs,  1.06... 


.24 
1.75 
1.52 


.42 


1.02 
8.70 


fS,0.02 

(P. trace 

(Ta,Cb)2O5,2.20 
Cb205,  trace... 


100.67 
99.76 
72.45 
99.73 
100.52 
101.08 
99.69 
100.33 
100.73 


L52 
.26 


.79 


14.68 


CbjOs,  0.76 . 
AI2O3I.34. 


99.79 
99.90 
100.60 

99.96 
98.72 
100.00 
100.25 
99.70 


68 .  Ferberite  from  Limoges,  probably  from  Puy-les-Vignes.  (See  Lacroix,  A . ,  Mineral 
logie  de  la  France  et  de  see  colonies,  vol.  4,  pt.  1,  p.  285,  footnote,  1910.)  Ebelmen, 
J.  J.,  Note  sur  la  composition  du  wolfram:  Annales  des  mines,  4tli  ser.,  vol.  4,  p.  407, 
1843. 

69.  Ferberite  from  Traversella,  Italy.  Bernoulli,  F.  A.,  Ueber  Wolfram  und 
einige  seiner  Verbindungen:  Poggendorf's  Annalen,  4tli  ser.,  vol.  21,  p.  603,  1860. 

70.  Ferberite  from  Nagpur  district,  India.  Analysis  by  Carnegie  Steel  Co.  Quoted 
by  Fermor,  L.  L.,  Note  on  an  occurrence  of  wolfram  in  the  Nagpur  district,  Central 
Provinces:  India  Geol.  Survey  Records,  vol.  36,  pt.  4,  p.  309,  1908. 

71.  Ferberite  from  Estremadura,  Spain.  Analysis  by  Truchot  quoted  by  Mennicke, 
Hans,  Die  Metallurgie  des  Wolfram,  p.  18,  1911. 

72.  Ferberite  from  Inverell,  County  Gough,  New  South  Wales.  Liversidge,  A., 
The  minerals  of  New  South  Wales,  p.  85,  1888. 

73.  Ferberite  from  Grube  Meiseberg,  Neudorf,  Harz  Mountains,  Germany.  Schnei- 
der, R.,  Ueber  die  chemische  Constitution  des  Wolfram-Minerals:  Jour,  prakt.  Chemie, 
vol.  49,  p.  334,  1850. 

74.  Ferberite  from  the  Bismuth  mine,  Torrington,  New  South  Wales.  Analysis 
by  H.  P.  White  quoted  by  Came,  J.  E.,  The  tungsten  mining  industry  in  New  South 
Wales:  New  South  Wales  Geol.  Survey  Min.  Res.  No.  15,  p.  70,  1912. 

75.  Ferberite  from  Gordon  Gulch,  Boulder  County,  Colo.  Analysis  quoted  as 
having  been  made  by  the  Colorado  Tungsten  Corporation.  George,  R.  D.,  The  main 
tungsten  area  of  Boulder  Coxmty,  Colo.:  Colorado  Geol.  Survey  First  Rept.,  p.  43, 
1909. 

76.  Ferberite  from  Grube  Meiseberg,  Neudorf,  Germany.  Schneider,  R.,  Ueber 
die  chemische  Constitution  des  Wolfram-Minerals:  Jour,  prakt.  Chemie,  vol.  49,  p. 
334, 1850. 

77.  Ore  from  Beaver  Creek,  Boulder  County,  Colo.  Analysis  given  by  Greenawalt, 
W.  E.,  The  tungsten  deposits  of  Boulder  County,  Colo.:  Eng.  and  Min.  Jour.,  vol. 
83,  p.  951,  1907.  The  analysis  also  gives:  Gold,  trace;  silver,  1.2  ounces  to  the  ton. 
The  item  given  under  SiOj  is  designated  in  the  original  as  "Si." 

78.  Ferberite  from  Cave  Creek,  Maricopa  County,  Ariz.,  U.  S.  Nat.  Mus.  catalogue 
No.  87283.    Analysis  by  Edgar  T.  Wherry.    The  mineral  is  black  and  opaque.    The 


COMPOSITION  OF  FERBERITE  AND  OTHER  MEMBERS  OP  SERIES.       33 
the  wolframite  aeries — Continued. 


No. 

Recalculated  analysis. 

SpeciAo 
gmvity. 

WO,. 

FeO. 

MnO. 

FeWO<. 

ItnWOi. 

Excess 
FeO. 

Excess 
WO,. 

0aWO4. 

68 
69 
70 
71 
72 
73 
74 
75 
76 

n 

?l 

80 

81 
82 
83 

84 
85 

76.4 

76.4 

76.4 

76.4 

76.3 

76.3 

76.  ,35 

76.3 

76.4 

76.3 

76.3 
76.3 
76.3 

76.3 
76.3 
76.3 
76.3 
76.3 

19.1 
19.2 
19.3 
19.3 
19.4 
19.5 
19.7 
19.8 
19.8 

19.9 

20.0 
20.0 
20.5 

20.5 
21.0 
21.3 
22.3 
22.8 

4.5 
4.4 
4.3 
4.3 
4.3 
4.2 
3.95 
3.9 
3.8 

3.8 

3.7 
3.7 
3.2 

3.2 
2.7 
2.4 
1.4 
.9 

80.8 
81.1 
81.5 
81.7 
81.8 
82.1 
83.1 
83.4 
83.6 

84.0 
84.2 
84.3 
86.4 

86.6 
88.7 
89.6 
94.2 
96.1 

19.2 
18.9 
18.5 
18.3 
18.2 
17.9 
16.9 
16.6 
16.4 

16.0 

15.8 
15.7 
13.6 

13.5 
11.3 
10.4 
5.8 
3.9 

0.1 
1.4 
1.5 
4.2 

• 

20.7 

3.7 

1.1 

2.0 

.6 

1.8 

1.0 

.8 
.8 

7.0 

3.1 

1.2 
9.0 

7.8 

7.182 

5.4 

6.801 

2.4 
5.4 

8.7 

.6 

1.0 

2.3 

7.8 
1.3 

7.169 

6.405 

7.334 

4.1 

analysis  shows  also  CuO,  1.34;  "TajOg,  approximately  1.50,  and  CbjOj,  0.70,  judging 
from  density  of  oxides. "  The  quantity  of  tantalic  and  columbic  pentoxides  indicated 
is  unusually  high.  The  excess  WO3  shown  seems  to  be  combined  with  part  of  the 
CuO  to  form  a  hydrous  copper  tungstate  new  to  science.  Work  is  now  being  under- 
taken on  this  mineral.  Part  of  the  copper  is  probably  combined  with  the  SiOj  as 
chrysocolla. 

79.  Ferberite  from  the  Sierra  Almagrera,  southern  Spain.  Liebe,  K.  L.  T.,  Ein 
neuer  Wolframit;  ein  Beitrag  zur  Mineral-Chemie:  Neues  Jahrb.,  1863  p.  645,.  The 
analysis  also  shows  AI2O3,  1.15;  limonite,  1.39;  SnOj,  0.14;  GIO,  trace.  The  analysis 
Bs  given  follows  Dana's  recalculation  after  subtracting  the  limonite  (System  of 
Mineralogy,  p.  985).  The  specific-gravity  determination  is  stated  to  have  been 
made  by  Breithaupt. 

80.  Ferberite  from  Kootenay  Belle  mine,  Salmo,  British  Columbia.  Walker,  T.  L., 
Report  on  the  tungsten  ores  of  Canada:  Canadian  Dept.  Mines,  Mines  Branch,  p.  38, 
1909. 

81.  Ferberite  from  the  American  Tungsten  Co.'s  mine,  BUU  City,  S.  Dak.  Analysis 
made  at  the  South  Dakota  School  of  Mines.  Quoted  by  C.  H.  Fulton  in  a  private 
report  on  the  mine.  Traces  of  SnOj  and  S  were  found.  If  the  quantities  given  are 
otherwise  correct,  it  seems  probable  that  a  part  of  the  substance  determined  as  "SiOa  " 
is  really  CaO;  hence  the  excess  of  WO3. 

82.  Ferberite  from  the  Sierra  Almagrera,  southern  Spain.  Rammelsbeig,  C.  F., 
Ueberdie  chemische  Zusammensetzung  des  Ferberits:  K.  preuss.  Akad.  Wiss.  Ber- 
lin Monatsber.,  p.  175,  1865. 

83.  Ferberite  from  Adun-Tschilon,  Siberia.  Average  of  four  analyses.  Beck,  W., 
and  Teich,  N.,  Ueber  Wolfram  und  Scheelit  aus  Fundorten  Russlands:  Russ.-k. 
mineral.  Gesell.  St.  Petersburg  Verb.,  2d  ser.,  vol.  4,  p.  315,  1869. 

84.  Ferberite  from  Ivigtut,  Greenland.  Analysis  by  Chr.  Christensen.  Boggild, 
0.  B.,  Mineralogia  Groenland  (Saertryke  af  Meddelelser  om  Gronland,  vol.  32):  Min- 
eral, and  Geol.  Mus.  Univ.  Copenhagen,  Contr.  to  Mineralogy  No.  6,  p.  182,  1905. 

85.  Ferberite  from  Last  Chance,  Boulder  County,  Colo.  Analysis  by  J.  B.  Ekeley. 
George,  R.  D.,  The  main  tungsten  area  of  Boulder  County,  Colo.:  Colorado  Geol. 
Survey  thirst  Rept.,  p.  42,  1909. 

35659°— Bull.  583—14 3 


M  COLORADO  FERBERITE  AND  THE   WOLFRAMITE   SERIES. 

Analyses  of  minerah  oj 


Locality. 

\ 

Oiigliialai^alysis. 

Ma 

wc 

^ 

MnO. 

c»o. 

SIO* 

MgO. 

Other  sab- 
sumoes. 

Total. 

M 

1f«MliK.fMn  

7LM    2I.» 
<L15     12.3S 
73.52    22.65 
74.13    23.15 
72.24     27.19 
«5.88    24.14 
7L01     24.S2 
7S.214   24.371 
«0lS8     19.13 
7S.47    24.33 

a«7 

.51 

.60 

.56 

,57 

.37 

.18 

.185 

.06 

0.60 
.38 
.42 

1.28 

'".'35" 
1.32 

a49 
16.10 
1.81 

.71 

Tnkoe. 

6.45 

.71 

0.12 
.39 

Al,O,0.25.... 
AljO,2.49.... 
Al,O,0.75.... 
AltO,0.46.... 

99.92 
100.35 

99.75 
100.29 
100.00 

99.88 
100.59 

99.77 
100.26 

99.80 

X7 

oSS^Sa^Oolo. 

n 
m 

STiS^Cblo 

IbKtaS  Lake.  Goto 

SSSS^S^r.::: 

fi 

.50 

.59 
Trace. 

Al,0,2.19.... 
AljO,2.25.... 

fli 
n 

WtaMi«80BklB.CQto 

JOH                          

M 

;;£i;.i-i^  «va« 

.44 

TnoL 

15,94 

Al,O,3.10.... 
TajO*,  trace.... 

ti 

vSIii.,  ^;.r« 

86.  Fefberite  from  Magnolia,  Boulder  Coonty,  Colo.  Analysb  by  J.  B.  Ekeley. 
Goofge,  R.  D.,  The  main  tungsten  area  of  Boulder  County,  Colo.:  Colorado  Geol. 
Survey  First  Rept.,  p.  42, 1909. 

87.  Ferberite  from  Clyde  Mine,  Nederland,  Boulder  County,  Colo.  Analysis  by 
Ekeley,  J.  B.,  'nie  compoation  of  some  Colorado  tungsten  ores:  Colorado  Univ. 
Studies,  vol.  6,  No.  2,  p.  95, 1909. 

88.  F«berite  from  Elsie  mine,  Boulder  County,  Colo.  Analysis  by  J.  B.  Ekeley. 
Get^ge,  R.  D.,  The  main  tungsten  area  of  Boulder  County,  Colo.:  Colorado  Geol.  Sur- 
yej  Fint  Bept.,  p.  42, 1909. 

89.  F«bmte  from  claim  near  Manchester  Lake,  Gilpin  Coimty,  Colo.  Analysis  by 
J.  B.  Ekeley.  George,  R.  D.,  The  main  tungsten  area  of  Boulder  Coimty,  Colo.: 
Oolocado  Geol.  Sur\ey  First  Rept.,  p.  42,  1909. 

90.  Ferberite  from  Puy-les-Mgnes,  France.  Analysis  by  Nicolardot  quoted  by 
Lacraix,  A.,  Min^ralogie  de  la  France  et  de  ses  colonies,  vol.  4,  pt.  1,  p.  282,  1910. 
Xhe  anatyas  Aawe  a  trace  of  SnO,. 


COMPOSITION  OF  FERBERITE  AND  OTHER  MEMBERS  OF  SERIES.       35 
the  wolframite  series — Continued. 


No. 

Recalculated  analysis. 

Spedflo 
gravity. 

WO,. 

FeO. 

MnO. 

FeWO<. 

MnWO<. 

Excess 
FoO. 

Excess 
WO,. 

CaWO<. 

86 
87 
88 
89 
90 
91 
92 
93 
94 
95 

76.3 
.76.3 
76.3 
76.3 
76.3 
76.3 
76.3 
76.3 
76.3 
76.3 

23.0 
23.0 
23.1 
23.1 
23.1 
23.3 
23.5 
23.5 
23.6 
23.7 

0.7 
.7 
.6 
.6 
.6 
•4 
.2 
.2 

96.9 
97.2 
97.3 
97.4 
97.5 
98.1 
99.1 
99.2 
99.6 
100.0 

3.1 
2.8 
2.7 
2.6 
2.5 
1.9 

.9 
8 

.4 

2.3 
1.3 
1.1 
1.5 
5.3 
4.5 
4.6 
1.2 
.2 
.8 

3.1 
1.9 
2.6 
6.6 

6.8 

7.079 

2.8 

6.640 

91.  Ferberite  from  the  Barker  ranch,  Nederland,  Boulder  County,  Colo.  Analysis 
by  J.  B.  Ekeley.  George,  R.  D.,  The  main  tungsten  area  of  Boulder  County,  Colo.: 
Colorado  Geol.  Survey  First  Rept.,  p.  42,  1909. 

92.  Ferberite  from  Winnebago  mine,  Gilpin  County,  Colo.  Analysis  furnished  by 
E.  M.  Green,  Rollinsville,  Colo.  The  original  gives:  FeO,  22.11,  and  FejOa,  3.01. 
The  ferric  oxide  has  been  calculated  to  its  equivalent  of  ferrous  oxide,  and  this  seems 
to  accord  better  with  the  remainder  of  the  analysis. 

93.  Analysis  of  a  pseudomorph  of  ferberite  (reinite)  after  scheelite  from  Otomezaka 
or  Kurasawa,  Japan,  by  F.  Kodera.  Quoted  by  Tsunashiro  Wada,  Minerals  of  Japan 
(translated  by  Takudzi  Ogawa),  p.  77,  1904. 

94.  Ferberite  from  Conger  mine,  Nederland,  Boulder  County,  Colo.  Analysis  by 
Ekeley,  J.  B.,  The  composition  of  some  Colorado  tungsten  ores:  Univ.  Colorado 
Studies,  vol.  6,  p.  95,  1909. 

95.  Ferberite  (reinite)  replacing  scheelite,  from  Kimbosan,  Kei,  Japan.  Analysifi 
by  E.  Schmidt.  Quoted  by  Luedecke,  Otto,  Ueber  Reinit,  K.  v  Fritsch,  Einneues 
Wolframsaures  Eisenoxydul:  Neues  Jahrb.,  1879,  p.  288. 


36  COLORADO   FERBERITE   AND   THE   WOLFRAMITE   SERIES. 

CONSIDERATION  OF  THE  ANALYSES. 

The  collection  of  analyses  just  given  indicates  an  essentially 
complete  series  of  mixtures  of  manganese  and  iron  tungstates  ranging 
from  pure  manganese  tungstate  to  pure  iron  tungstate,  with  the 
possible  number  of  members  limited  only  by  the  number  of  speci- 
mens analyzed  and  by  the  accuracy  of  the  determinations.  The 
series  is  analogous  to  those  of  the  plagioclase  feldspars  and  the 
columbite-tantalite  group.  The  greatest  difference  between  consecu- 
tive analyses  in  either  hiibnerite  or  wolframite  molecules  is  5.5  per 
cent,  which  is  found  between  the  wolframites  from  Lost  River, 
Alaska  (No.  34),  and  Vilate,  France  (No.  35),  which  contain,  respec- 
tively, as  recalculated,  56.7  per  cent  and  51.2  per  cent  MnW04,  but 
there  can  be  little  doubt  that  analyses  of  other  specimens  from  these 
or  other  localities  would  fall  within  the  gap.  It  is  also  probable  that 
if  the  exact  quantity  of  iron  and  manganese  combined  as  tungstates 
were  known,  the  results  would  be  considerably  different.  Most 
writers  on  the  subject  have  treated  the  woKramites  as  definite  com- 
pounds of  FeW04  a^d  ^InW04,  bearing  relations  to  each  other  which 
could  be  expressed  by  small  whole  numbers,  but  this  does  not  seem 
to  be  borne  out  by  the  analyses.  Groups  of  analyses  of  woKramites 
from  Zinnwald,  from  the  Boulder  district,  and  from  the  Black  Hills, 
all  small  areas,  show  a  very  considerable  variation  in  the  ratio  of 
iron  and  manganese  bearing  molecules.  Those  from  Zinnwald  range 
from  77.0  per  cent  to  60.2  per  cent  MnW04,  and  those  from  Boulder 
County  range  from  36.2  per  cent  to  0.4  per  cent  MnWO^.  In  some 
crystals  of  hubnerite  a  considerable  variation  in  color,  probably  due 
to  difference  in  composition  of  different  zones,  can  be  seen.  Were 
it  not  for  the  black  color  of  each  part,  a  zonal  growth  similar  to 
that  of  porphyritic  plagioclase  feldspars  could  probably  be  observed  in 
many  wolframite  crystals.  (See  PI.  XIII,  p.  30.)  As  stated  in  another 
place  by  W.  T.  Schaller,  no  difference  in  crystal  form  can  be  noticed 
between  the  two  ends  of  the  series.  If  there  were  a  series  of  definite 
compounds  between  the  two  end  members,  some  expression  of  the  fact 
would  probably  be  found  in  the  facial  angles. 

Attention  is  called  to  the  number  of  wolframites  whose  analyses 
show  the  presence  of  tantalum  and  columbium.  It  is  probable 
that  in  some  analyses,  particularly  the  earlier  ones,  other  substances 
have  been  determined  as  these  elements,  and  in  other  analyses  they 
have  not  been  recognized  or  determined  when  present.  Dr.  Eberhard 
showed  spectroscopicaUy  (p.  18)  that  columbium  was  present  in  a 
specimen  of  Boulder  County  ferberite,  but  he  made  no  test  for 
tantalum.  Where  one  element  is  present,  however,  the  other  is 
almost  sure  also  to  be  there. 


DEFINITION  OF  FERBERITE  AND  OTHER  MEMBERS  OF  THE  SERIES.       37 

Tantalum  and  colunibium  are  common  in  wolframites  and  their 
commercial  possibilities  have  been  investigated  rather  extensively.* 
Mennicke  mentions  1.5  per  cent  as  the  highest  content  of  the  oxides 
known  in  wolframites,  but  the  ferberite  from  Cave  Creek,  Ariz., 
carries  2.2  per  cent  of  the  combined  Ta^Og  and  CbjOj,  according  to 
Wherry's  analysis.  The  form  in  which  these  oxides  are  present  is 
not  positively  known,  but  it  seems  probable  that,  as  suggested  by 
Damour,^  they  occur  as  minute  particles  of  columbite.  In  the 
ferberite  of  Cave  Creek  irregularities  in  cleavage  faces  seem  to  be  due  to 
the  presence  of  small  bodies  of  a  different  black  opaque  mineral  which 
may  be  columbite.     I  hope  to  do  further  work  upon  this  subject. 

DEFINITION   OF  FERBERITE  AND    OTHER   MEMBERS    OF 
THE    WOLFRAMITE    SERIES. 

The  continuity  of  the  wolframite  series  as  indicated  by  the  analyses 
quoted  shows  that  its  customary  division  into  hiibnerite,  wolframite, 
and  ferberite  must  of  necessity  be  arbitrary.  The  analysis  on  which 
the  species  ferberite  is  based  (No.  79)  gives  a  content  of  3.02  per  cent 
MnO,  equivalent  to  3.7  per  cent  MnO  or  15.7  per  cent  MnWO^  after 
recalculation.  Great  accuracy  can  not  be  claimed  for  the  figures 
showing  the  constituent  molecides,  as  the  material  was  impure.  In 
defining  the  species  it  can  hardly  be  held  that  3.07  per  cent  MnO  or 
15.7  per  cent  MnWO^  must  mark  the  extreme  limit  of  Mn  allowable  in 
ferberite.  As  by  common  usage  the  wolframite  series  is  divided  into 
three  groups,  20  per  cent  MnWO^  seems  to  be  a  convenient  and 
reasonable  limit  to  place  upon  the  MnWO^  allowable  in  a  ferberite,  and 
convenience  would  seem  to  indicate  for  hiibnerite  a  similar  limit  of  20 
per  cent  for  its  content  of  iron  tungstate,  FeWO^.  For  the  mixtures 
between  these  end  members  the  older  term  wolframite  may  properly 
be  retained,  and  this  term  may  well  serve  also  as  a  general  or  field  name 
for  the  members  of  the  series  which  can  not  be  definitely  identified. 

I  therefore  piopose  the  following  definitions  for  the  members  of  the 
wolframite  series: 

Ferberite :  A  monoclinic  iron  tungstate  having  when  pure  the  com- 
position FeWO^.  It  may  contain  not  more  than  20  per  cent  of  the 
hiibnerite  molecule,  MnW04. 

Hiibnerite :  A  monoclinic  manganese  tungstate  having  when  pure 
the  composition  MnWO^.  It  may  contain  not  more  than  20  per 
cent  of  the  ferberite  molecule,  FeWO^. 

>  Mennicke,  Hans,  Die  Metallurgie  des  Wolframs,  pp.  125-130, 1911. 

*  Damour,  A.,  Sur  le  wolfram  tantalif^re  du  d^partement  de  la'  Haute-Vienne:  Soc.  g(k>l .  France  BulL, 
^  ser.,  p.  108, 1848. 


38  COLOKADO    FEKBERITE    AND    THE    WOLFRAMITE    SERIES. 

Wolframite:  A  monoclinic  mineral  containing  the  ferberite  mole- 
cule (FeW04)  and  the  hiibnerite  molecule  (MnW04)  in  all  propor- 
tions between  20  per  cent  FeWO^  and  80  per  cent  MnWO^,  and  80 
per  cent  FeW04  and  20  per  cent  MnW04. 

Under  this  scheme  the  analyses  show  ferberites  from  13  widely 
separated  localities — Boulder  County,  Colo.,  Cave  Creek,  Ariz.,  and 
Hill  City,  S.  Dak.,  in  the  United  States;  British  Columbia;  Greenland; 
France;  Saxony;  Italy;  Sierra  Almagrera  and  Estremadura,  Spain; 
New  South  Wales;  India;  Siberia;  and  Japan.  The  ferberite  of  Japan 
was  described  as  reinite  and  replaces  scheeHte.  From  Limoges, 
France  (No.  68),  is  shown  a  ferberite  that  contains  nearly  the  maxi- 
mum amount  of  manganese.  The  purest  ferberite^  showing  no 
manganese  and  only  a  small  excess  of  iron  oxide  (0.8  per  cent)'7is 
^^°^  f{(MftJ"p^"^  Mnerals  from  Gordon  Gulch  (No.  58)  and  Ward 
(No.  49),  in  the  Boulder  tungsten  field,  fall  well  within  the  wolfram- 
ites, although  from  the  most  remarkable  ferberite  locality  known. 
They  merely  emphasize  the  characteristic  variability  of  the  hiibnerite- 
ferberite  mixture. 

EXCESS   OF  FERROUS  OXIDE  AND  MANGANOUS  OXIDE. 

'  A  point  to  which  considerable  importance  has  been  attached  by 
different  writers  is  the  excess  of  FeO  in  the  ferberites,  but  the  table 
of  analyses  shows  that  they  are  not  unique  in  this,  though  some 
ferberites  do  carry  large  excesses  of  FeO. 

The  proneness  of  WO3  to  form  a  lower  oxide  on  heating  and  its 
solubility  make  it  seem  probable  that  many  determinations  of  the 
oxide  are  low,  so  that  the  appearance  of  an  excess  of  0.1  or  0.2  per 
cent  FeO  may  be  neglected.  It  is  also  probable  that  in  many  of  the 
analyses  the  MnO  is  too  high,  a  common  error  when  the  determina- 
tion is  made  gravimetrically,  and  a  very  small  excess  of  MnO  would 
cause  a  somewhat  larger  apparent  excess  in  the  FeO.  Only  a  few 
of  the  analyses  show  the  presence  of  alumina,  but  many  wolframites 
occur  in  a  gangue  containing  muscovite  or  feldspar  or  both,  and 
small  quantities  are  likely  to  be  mixed  with  the  mineral  analyzed. 
If  the  mineral  is  fused,  the  alumina,  unless  specially  separated,  will 
be  precipitated  with  the  iron  oxide,  and,  if  the  iron  is  determined 
gravimetrically,  will  by  so  much  make  it  appear  larger. 

Iron  oxide  is  commonly  present  as  such,  for  in  the  oxidized  zone  the 
breaking  down  of  minerals  such  as  siderite,  pyrite,  chalcopyrite,  or  wolf- 
ramite setsfree  iron  oxide,  which  mayformfilms  over  the  residual  wolf- 
ramite or  fill  cavities  of  microscopic  or  larger  size.  A  cut  and  polished 
crystal  of  brown  ferberite  from  the  Winnebago  claim  near  Rollins- 
ville  shows  a  very  porous  structure  (see  PL  IV,  ^;  p.  13)  and  the 
cavities  are  coated  with  hydrous  iron  oxide.  This  material  is  similar 
to  that  found  on  part  of  the  Rogers  tract  and  would  surely  give  a 


EXCESS    OP    FERROUS    OXIDE    AND    MANGA'NOUS    OXIDE.  39 

considerable  excess  of  iron  on  analysis.  Specular  hematite  or 
magnetite,  in  particles  too  small  to  be  easily  distinguished,  may  occur 
in  the  ore,  and  the  presence  of  one  or  both  of  these  minerals  may 
account  for  the  surplus  iron  shown  in  some  determinations. 

In  those  wolframites  whicli  contain  tantalum  and  colunibiuin 
colum])i1(^  may  fui-nis1i  m  ])nil  of  \]\o  appaiciit  cxcoss  of  iron.  Micro- 
scopic  examinations  made  hy  icIlecU'd  liglit  on  ])()nshe(l  and  etched 
specimens  of  clean  black  ferberite  show  none  of  the  differences  in 
texture  to  be  expected  if  such  other  minerals  were  present.  There 
are,  however,  minute  cavities  which  may  be  partly  filled  with  iron 
minerals.  Manganese  dioxide,  though  in  less  quantity  than  iron 
oxides,  is  commonly  associated  with  the  ores,  but  its  presence  on  the 
lighter-colored  hiibnerites  should  be  easily  distinguishable.  The 
possibility  of  FeO  and  MnO  being  held  in  solid  solution  in  the  minerals 
of  the  wolframite  series  suggests  itself,  but  no  proof  of  this  has  been 
found. 

It  is  to  be  noted  that  if  the  analyses  given  had  been  recalculated 
by  first  satisfying  the  FeO  with  WO3,  and  then  combining  the 
remainder  of  the  WO3  with  the  ^InO,  the  excess  of  the  FeO  would 
disappear  in  most  of  the  analyses  and  there  would  be  an  excess  of 
MnO.  However,  as  just  stated,  manganese  oxide  occurs  with  the 
wolframites  in  much  less  quantity  than  iron  oxide,  and  for  this  reason 
in  recalculating  an  analysis  it  is  best  to  first  satisfy  the  MnO  with 
WO3.  It  appears,  therefore,  that  though  some  of  the  woLframitesI 
may  carry  an  excess  of  FeO,  and  a  few  an  excess  of  both  FeO  and! 
MnO,  most  if  not  all  of  the  apparent  excesses  are  due  to  impurities] 
present  in  the  material  analyzea  and  to  errors  of  anjiTysis. 

Many  careful  analyses  of  well-selected  minerals  and  many  examina- 
tions by  metallographic  methods  must  be  made  before  a  real  excess 
of  FeO  or  MnO  in  the  wolframites  can  be  demonstrated. 


CRYSTALLOGRAPHY  OF  FERBERITE  FROM  COLORADO. 


By  Waldemar  T.  Schaller. 


PREVIOUS    PUBLICATIONS. 

The  several  papers  mentioned  by  Mr.  Hess  in  his  part  of  this  report 
give  some  general  facts  in  regard  to  the  habit  and  size  of  crystals  of 
ferberite.  Two  other  papers,  by  Warren  and  by  Moses  (see  Bibliog- 
raphy, pp.  74-75),  give  descriptions  of  ferberite  crystals  which  may 
have  come  from  this  locahty.  The  crystal  figured  by  Warren  is  said 
to  have  come  from  South  Dakota,  though  he  states  that  the  exact 
locality  could  not  be  ascertained.  From  the  appearance  of  the  crystal 
it  is  more  Ukely  to  have  come  from  Colorado  than  from  South  Dakota. 
The  crystal  figured  and  described  by  Moses  as  crystallized  wolframite 
from  Boulder  County,  Colo.,  is  very  similar  to  those  here  described. 

These  two  papers  are  the  only  publications  on  the  crystallography 
of  the  ferberite  from  Colorado  that  could  be  found. 

GENERAL    CHARACTER    OF    THE    CRYSTALS. 

MODE    OP   OCCUIIBENCE. 

In  the  specimens  examined  the  ferberite  crystals  are  perched  on 
the  country  rock  in  groups  or  they  fine  or  nearly  fill  the  cavities  or 
fissures  in  the  matrix.  Layers  of  ferberite  several  centimeters  thick, 
consisting  of  crystals  whose  bases  have  coalesced,  are  found  on  the 
rock.  Much  of  the  ferberite,  which  at  first  glance  seems  to  be  mas- 
sive, is  found  on  closer  inspection  to  be  a  granular  compact  mass  of 
small  crystals. 

The  crystals  occur  isolated  as  distinct  individuals  (Pis.  VII,  p.  18, 
and  VIII,  p.  19),  in  groups  of  parallel  or  nearly  parallel  individuals 
(Pis.  IX,  p.  20,  and  X,  p.  21),  or  in  confused  masses  consisting  of 
numerous  abutting  and  even  penetrating  crystals.  Twins  are  com- 
mon, though  single  untwinned  crystals  are  far  more  plentiful.  The 
nearly  parallel  groupings  are  of  two  kinds:  (1)  A  group  of  flattened 
crystals  which  may  depart  several  degrees  from  strict  parallehsm  and 
which  are  joined  by  the  a(lOO)  faces  (fig.  1);  and  (2)  crystals  joined 
by  the  c(OOl)  faces  and  superposed,  the  fine  of  demarcation  of  the 
40 


GENERAL  CHARACTER  OF   THE  CRYSTALS. 


41 


(liflerent  crystals  being  well  shown  by  the  irregular  lines  crossing 
the  prism  zone  normal  to  the  vertical  striations  (fig.  2).  The  distri- 
bution of  the  dome  faces  on  several  of  the  parallel  groupings  joined  by 
the  a  (100)  face  conclusive- 
ly demonstrates  that  the 
crystals  are  not  twinned. 

Well-developed  crys- 
tals are  abundant,  but 
many  crystals  are  rounded 
and  curved  either  in  a 
single  zone  or  throughout. 
The  curving  of  the  sur- 
faces in  a  single  zone  is 
generally  due  to  the 
marked  development  of 
the  striations  in  the  prism 
zone.  (See  fig.  9,  p.  59.) 
The  curving  of  the  faces 
over  an  entire  crystal  is 
due  to  the  nearly  parallel 
grouping  of  a  number  of  crystals,  each  one  deviating  successively  a 
little  more  from  parallelism  with  the  original  unit. 

The  various  forms  of  occurrence  of  ferberite  found  on  the  specimens 
examined  may  conveniently  be  summarized  as  follows : 

1,  Massive. 

2,  Bladed,  indistinctly  crystallized. 

3,  Distinct  individual  crystals. 

a,  Single  well-formed  crystals  (Pis. 
VII,  VIII,  XI,  and  XII, 
and  text  figs.  3-34). 

b,  Twinned  crystals  (PL  VIII,A,  and 
textfigs.  14, 15, 17,andl8). 

c,  Crystals  grouped  in  parallel  po- 
sition (Pis.  IX  and  X). 

(1),  Composition  face  a(lOO) 
(fig.  1). 

(2),  Composition  face  c(OOl) 
(fig.  2). 

d,  Rounded    crystals  or   groups   of 
crystals. 

SIZE. 


FiGXTBE  1  .—A ,  Orthographic  projection  of  crystals  with  similar 
combinations  in  parallel  grouping,  joined  by  the  a(lOO)  face; 
B,  Orthographic  projection  of  two  crystals  with  dissimilar 
combinations.  The  cleavage  parallel  to  6(0l0)  in  many  crys- 
tals terminates  one  side.  Forms:  c{001},  6{010},  g{100>, 
7n<110},  /{210>. 


Figure  2.— Superposed  crystals,  joined  by 
the  c(OOl)  faces.  The  line  of  demarcation 
is  normal  to  the  vertical  striations  on  the 
large  a(lOO)  faces. 


In  size  the  crystals  vary  considera- 
bly. The  largest^  seen  were  about 
1.5  centimeters  long  (6  axis),  half  as  high  (c  axis).  an3  al)out  TrnilTr- 
gieters"tEicE^TS"axis) .  The  general  average  would  be  aboutS  to  lOmilh- 
meters  long,  2  to  5  millimeters  high,  and  1  to  3  millimeters  thick.     On 


42  COLOKADO   FERBERITE   AND   THE   WOLFRAMITE   SERIES. 

some  of  the  rock  specimens  areas  extending  over  many  square  centi- 
meters are  coated  by  minute  crystals,  few  of  which  measure  more  than 
a  miUimeter  in  any  direction.  Most  of  the  crystals  measured  were 
much  smaller  than  the  average.  The  dimensions  of  the  crystals  were 
accurately  measured  under  the  microscope,  so  that  their  proportions 
might  be  shown  in  the  drawings  for  the  text  figures  in  this  bulletin. 
Of  18  crystals  thus  accurately  measured  the  a  axis  lay  between  0.3  and 
0.7  millimeter  on  14  crystals;  the  h  axis  (which  in  most  of  these  crys- 
tals has  about  half  the  true  original  value)  between  0.5  and  2.5  milli- 
meters on  16  crystals;  and  the  c  axis  between  1.0  and  3.  5  millimeters 
on  13  crystals.  The  extreme  values  are:  a  axis,  0.3  to  5.0  millimeters 
(the  5.0  is  an  extreme  value,  the  next  highest  is  only  1.5;  all  the  other 
values  are  less  than  1.0  millimeter);  h  axis,  0.6  to  3.2  milhmeters;  c 
axis,  0.3  to  3.8  millimeters. 

Most  of  the  crystals  measured  were  bounded  on  one  side  by  a  cleav- 
age face  of  &(010),  so  that  the  sizes  here  given  do  not  actually  repre- 
sent the  size  of  the  original  crystals  in  the  direction  of  the  h  axis.  In 
the  illustrations  (figs.  3  to  34)  the  crystals  are  generally  shown  rela- 
tively longer  in  the  h  axis  than  the  measured  values  indicate,  in  order 
to  represent  more  truly  their  actual  original  sizes.  The  h  axis  on 
many  of  the  complete  crystals  was  probably  twice  as  great  as 
measured. 

COLOR   AND   CLEAVAGE. 

The  crystals  are  black  and  their  luster  is  splendent,  nearly  metallic. 
The  streak  is  dark  brown,  suggesting  hematite.  It  is  distinctly  not 
JiTack.  Cleavage  is  cllnopinacoidal,  5(010} ,  very  good,  and  commonly 
visible  on  the  basal  pinacoid. 

THE  MEASURED  CRYSTALS  BY  LOCALITIES. 

In  the  following  table  the  crystals  measured  are  grouped  according 
to  the  mine  from  which  they  came.  In  addition  their  general 
character  and  habit  are  given  for  reference.  These  descriptions  and 
locahties  are  based  entirely  on  the  material  collected  by  Mr.  Hess. 
For  other  locahties,  not  mentioned  here,  the  papers  given  by  Mr.  Hess 
in  his  bibHography  should  be  consulted. 


AXIAL  ELEMENTS. 
Lut  of  crystals  by  localities. 


43 


Crj'S- 
tal 
No. 


Locality. 


Illus- 
trated In 
figure — 


Orifcinal 

note- 
book No. 


Description  and  habit.o 


Crystals  1-12  from  1  specin^n  of  ore  from  the 
100-foot  level  of  the  Hoosier  mine,  Boulder  County, 
Colo. 


Crystals  13-17  from  1  specimen  from  the  Nugpet 
i    claim,  5  miles  southeast  of  Nederland,  IJ  miles 
'    northeast  of  Rollinsville,   Gilpin  County,  Colo. 
Specimen  taken  from  a  17-foot  winze. 


Crystals  18-23, 24-25, 26-27 ,  from  three  differen  tspeci- 
■    mens,  all  from  the  sam  t  claim  as  crystals  13-17 
(Nugget  claim). 


Crystals  28-35  from  one  specimen  from  Tovm  Lot 
mine,  Nederland,  Boulder  County,  Colo. 


•From  Black  Hawk  claim,  Boulder  County,  Colo 

From  Georgia  A.  vein,  2  miles  northeast  of  Nederland, 
Boulder  County,  Colo. 


24 


Ai 
A, 

A, 

A4 

As 
A« 

At 
As 

A, 
A 10 
An 

A„ 

B, 
B, 
B, 

B4 

Bs 

Ci-1 
Ci-2 
Ci-3 
Ci-4 
Ci-5 
Ci-6 
C^l 
C^2 
Cs-l 
C3-2 

Cr-3 

Di 

D, 

D3 

D4 

Ds 

D« 

D; 

El 
E, 


8,  prismatic. 
8,  wedgelike. 
8,  prismatic. 
8,  wedgelike. 
8,  prismatic. 

Do. 

Do. 
8,  wedgelike. 
8,  prismatic. 
T,  tabular. 

Do. 

Do. 

8,  prismatic. 

Do. 

Do. 
G,  prismatic. 
8,  prismatic. 

Do. 

Do. 
G,  prismatic. 
S,  prismatic. 

Do. 
T,  tabular. 
8,  rhombic. 

Do. 

Do. 
T,  tabular. 

S,  tabular. 
S,  wedgelike. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

S,  cubic. 
Do. 

Do. 


a  S,  simple  crystal;  G,  group  of  crystals  In  nearly  parallel  position;  T,  twin  crystal. 

,  AXIAIi    EIjEMENTS. 

f    The  discussion  of  the  axial  elements  of  ferberite  leads  at  once  to  the 
question  of  the  relation  of  ferberite  to  the  wolframite  group. 

In  this  connection  a  consideration  of  the  relation  in  angidar  values 
between  the  pure  iron  tungstate  and  the  pure  manganese  tungstate 
is  of  interest.  The  ferberite  crystals  at  hand  did  not  yield  results  as 
satisfactory  as  had  been  expected,  because  of  the  imperfection  of  the 
crystals,  due  to  striations,  parallel  groupings,  and  hke  features; 
because  of  the  scarcity  of  well-developed  terminal  forms;  and  because 
the  high  poUsh  of  most  of  the  crystals  had  been  destroyed  by  the 
hydrofluoric  acid  used  to  remove  the  matrix  and  clean  the  crystals. 

CALCULATION  OP  VALUES. 

Below  are  given  the  best  measurements  obtained  that  are  suitable 
for  the  calculation  of  the  axial  elements,  and  these  are  compared  with 
the  measurements  given  in  the  literature  for  the  members  of  the 


44 


COLOKADO   FEKBEEITE   AND   THE   WOLFRAMITE   SERIES. 


wolframite  group.     All  measurements  were  made  with  a  Goldschmidt 
two-circle  goniometer. 

Average  of  best  measurements. 


(010)  :  (110) 

Fair  reflection: 
50°  16^ 
22 
23 
12 
24 
20 
22 
16 
15 

Poor  reflection: 
50°  31^ 
27 
28 
22 
17 
20 
21 

Average  of  9  measurements  with  fair 

reflection,  50°  19^ 
Average  of  7  measurements  with  poor 

reflection,  50°  24^ 
Average  of    the  16  measurement^/ 

50°  20i^ 

(001)  :  (Oil) 

Good  reflection: 
41°  00^ 

01 

00 
40    59 

59 

57 

57 

58 

56 

53 

56 

Average  of  11  measurements,  40°  58''. 


Average  of  4  measurements,  89°  37''. 

In  the  measurements  of  the  prism  angles  the  cj)  angle  was  obtained, 
this  being  the  same  as  the  angle  (010)    A  prism.     The  Vq  or  zero 

I  Good  measurements  weighted  twice  as  much  as  fair  ones;  fair  measurements  weighted  twice  as  much 
as  poor  ones. 


(010)  :  (210) 

Good  reflection: 
67°  27^ 
23 
24 
26 
25 
31 
25 
32 
21 

Fair  reflection: 
67°  17^ 
23 
16 
28 
19 
27 
30 
26 

Average  of  9  measurements  with  good 

reflection,  67°  26^ 
Average  of  8  measurements  with  fair 

reflection,  67°  23^ 
Average  of    the  17  measurements,^ 

67°  25^ 

(001)  :  (102) 


27°  46^ 

49 

27    43 

45 

37 

50 

Average  of  6  measurements. 

27° 

46^ 

(001)  :  (100) 

89°  50^ 

34 

32 

33 

AXIAL  ELEMENTS. 


45 


reading  on  6(010)  was  averaged  for  each  crystal  from  the  readings 
obtained  on  (010)  and  (010)  (often  a  cleavage  face),  and  from  the  aver- 
age of  (110)  and  (iTO),  and  (210)  and  (2T0),  respectively.  The  c(OOl) 
faces  were  generally  striated  in  the  zone  (001)  :  (100),  but  this  in 
nowise  interfered  with  the  accuracy  of  the  measurement  of  the  angle 
(001)  :  (Oil).  The  accurate  measurements  from  (001)  to  (102)  and 
to  (100)  were  very  few  in  number,  as  the  base  (001)  was  striated  in 
this  direction  on  most  of  the  crystals. 

COMPARISON   OF   VALUES. 

Instead  of  deriving  axial  elements  from  these  angular  values  I 
have  compared  the  interfacial  angles  directly  with  the  best  ones 
I  could  find  in  the  literature  for  the  entire  wolframite  group.  These 
have  been  arranged  in  order  of  decreasing  percentage  of  MnO,  so 
that  the  first  lines  in  the  table  below  represent  hiibnerite  and 
the  last  lines  (except  the  very  last)  represent  ferberite.  The  very 
last  line  contains  the  values  taken  from  Goldschmidt's  Winkel- 
tabellen,  in  which  the  axial  elements  of  Descloizeaux,  Krenner, 
and  Seligmann  have  been  averaged.  (See  Bibliography,  pp.  74-75.) 
A  careful  study  of  the  angular  values  given  in  any  column 
does  not  show  any  regular  increase  or  decrease  correspondiug 
with  the  regular  decrease  in  percentage  of  MnO.  In  fact  the  varia- 
tion in  angular  values  for  two  or  more  wolframites  of  nearly  the  same 
composition  is  nearly  as  great  as  between  the  extreme  end  members. 
The  correlation  of  the  chemical  composition  and  the  crystallographic 
constants  is  doubtful  in  so  far  as  the  analytical  figures  given  were 
not  obtained  on  the  material  actually  measured. 

Comparison  of  angles  with  variation  in  chemical  composition. 


Locality  and 

Author. 

Per 
cent 
MnO. 

Angle. 

material. 

(010):(110). 

(010):(210). 

(001):(011). 

(001):(lp2). 

(001):(100). 

MnW04    (arti- 
ficial). 
Megaba.'nte 

Groth  and  Arz- 
runi. 
..do 

23.4 

22.24 
21.93 
9.4 

4.96 
4.84 
3.15 

!o 

50  15 

50  27i 
50  06 
50  21 

50  30 
50  18i 
50  36 
50  204 
50  33 

50  27 

0        / 

Colorado 

Penfield.. 

67  19 

40  55 
40  51^ 

40  42J 

40  57 

41  03} 
4058 

27  12i 

89  07} 

MnjFej  (W04)5 

(artificial). 
Saxony 

Groth  and  Arz- 

runi. 
Krenner. . . 

67  36 
67  28 
67  40 
67  25 

27  29 
27  27i 
27  50i 
27  46 
27  33 

27  35 

89  m 

France 

Descloizeaux 

Seligmann 

W.T.Schaller.. 
Groth  and  Arz- 

runi. 
G  0 1  dschmidt's 

Winkeltabel- 

len. 

Spain. 

89  34 

Colorado 

FeW04     (arti- 
ficial). 
Average  o 

89  37 

67  34^ 

40  54 

89  32 

a  Computed  from  axial  elements  of  Descloizeaux,  Krenner,  and  Seligmann. 


46 


COLORADO   FERBERITE   AND   THE    WOLFRAMITE   SERIES. 


A  definite,  measured  difference  in  crystallographic  constants  be- 
tween ferberite  (FeW04)  and  hiibnerite  (Mn04)  is  not  shown  by  the 
table  just  given.  The  average  axial  elements  given  by  Goldschmidt 
represent  closely  the  angular  values  for  the  different  members  of  the 
wolframite  group.  These  values  are  also  close  to  those  obtained  on 
the  Colorado  ferberite  as  shown  below. 

Comparison  of  angles  of  ferberite  from  Colorado  with  the  values  given  in  Goldschmidt' s 

Tables. 


Angle. 

Gold- 
schmidt's 
Winkel- 
tabellen. 

Boulder 
County 
ferberite. 

Difference. 

(010):(110) 

(010):(210)...,... 

(001):(011) 

(001):(102) 

(001):(100) 

50  27 
67  34 
40  54 
27  35 
89  32 

50  m 
67  25 
40  58 
27  46 
89  37 

-06^ 

-09 

+04 

+11 

+05 

The  axial  elements  given  by  Goldschmidt,  namely,  a: 6:^  =  0.8255: 
1:0.8664,  ^  =  89°  32',  therefore  best  represent  the  constants  for  the 
entire  wolframite  group. 

The  data  for  the  percentages  of  manganese  given  in  the  table  on 
page  45  have  been  taken  from  Dana.^  Descloizeaux's  measurements 
were  made  on  material  from  Vilate,  near  Chanteloube  (Haute- 
Vienne),  France.  An  analysis  of  wolframite  from  Chanteloube  shows 
4.84  per  cent  MnO  and  19.32  per  cent  FeO.  Krenner's  measurements 
were  made  on  crystals  from  Ehrenfriedersdorf ,  Saxony,  and  an  analy- 
sis of  material  from  the  same  locality  shows  4.96  per  cent  MnO  and 
19.16  per  cent  FeO.  Seligmann's  ferberite  from  Sierra  Almagrera, 
Spain,  contains  3.15  per  cent  MnO  and  19.95  per  cent  FeO,  according 
to  Doelter.2  Two  confirmatory  analyses  of  the  Spanish  ferberite 
show  3.00  and  3.02  per  cent  MnO  with  high  FeO.  Hiibnerite  from 
Colorado^  showed  21.93  per  cent  MnO  and  2.91  per  cent  FeO. 
^'Megabasite"  from  Schlaggenwald  contained  22.24  per  cent  MnO 
and  3.74  per  cent  FeO. 

FORMS    AND    ANGLES. 

A  total  of  32  forms  were  determined  on  the  ferberite  crystals  from 
Colorado.  Of  these  12  are  new  for  the  wolframite  group.  These  32 
forms  are  given  in  the  table  below  with  the  measured  and  cal- 
culated coordinate  angles.  The  new  forms  are  marked  with  an 
asterisk  (*). 

1  Dana,  E.  S.,  System  of  mineralogy,  6th  ed.,  p.  984, 1892. 

2  Zeitschr.  Kryst.  Min.,  vol.  11,  p.  348,  1887. 

8  Penfield,  S.  L.;  see  Dana,  E.  S.,  op.  cit.,  pp.  983, 984. 


NEW   FORMS. 

List  of  forms  and  angles  onferberite  crystals. 
{New  forms  are  marked  with  an  asterisk.] 


No. 

Letter. 

Symbol. 

Measured. 

Calculated. 

Gold- 
Schmidt. 

MiUer. 

^ 

fi 

* 

P 

o         / 

O            1 

e        1 

0          1 

1 

c 

0 

001 

90  00 

0  23 

90  00 

028 

2 

b 

Ooo 

010 

0  00 

90  00 

000 

90  00 

3 

a 

ooO 

100 

90  12 

90  00 

90  00 

90  00 

4 

r 

oo2 

120 

33  49 

90  00 

31  12 

90  00 

5 

m 

oo 

110 

50  21 

90  00 

50  27 

90  00 

6 

I 

2oo 

210 

67  25 

90  00 

67  31 

90  00 

7 

*R 

Voo 

15.7.0 

69  00 

90  00 

68  56 

90  00 

8 

*C 

|oo 

940 

70  01 

90  00 

69  51 

90  00 

9 

*F 

|oo 

520 

71  39 

90  00 

71  44 

90  00 

10 

Q 

foo 

830 

73  19 

90  00 

72  48 

90  00 

11 

d 

3oo 

310 

74  47 

90  00 

74  37 

90  00 

12 

*G 

IS 

720 

76  45 

90  00 

76  44 

90  00 

13 

*M 

510 

80  30 

90  00 

80  38 

90  00 

14 

*N 

yoo 

6oo 

11.2.0 

81  35 

90  00 

81  28 

90  00 

15 

J 

610 

82  00 

90  00 

82  10 

90  00 

16 

*L 

7co 

710 

83  08 

90  00 

83  16 

90  00 

17 

n 

8oo 

810 

84  20 

90  00 

84  06 

90  00 

18 

/ 

01 

Oil 

0  04 

40  54 

0  32 

40  54 

19 

u 

+  10 

+  |o 

104 

90  00 

16  28 

90  00 

15  08 

20 

t 

102 

90  00 

27  46 

90  00 

28  03 

21 

*H 

+  10 

904 

90  00 

66  31 

90  00 

67  07 

22 

r 

;11 

1. 0.11 

90  00 

4  20 

90  00 

4  59 

23 

*B 

123 

31  10 

34  13 

31  47 

34  12 

24 

*E 

+AtV 

5.9.14 

34  25 

33  48 

34  31 

34  03 

25 

<o 

+ 1 

111 

50  25 

53  45 

50  40 

53  49 

26 

A 

+  i 

112 

50  16 

34  24 

50  53 

34  29 

27 

*A 

th 

337 

50  45 

30  37 

50  58 

30  31 

28 

V 

214 

69  42 

31  22 

67  53 

29  55 

29 

*D 

+ 1  § 

313 

74  21 

47  21 

74  44 

47  38 

30 

s 

-12 

121 

39  14 

63  45 

31  00 

63  41 

31 

e 

-  i 

112 

50  16 

34  27 

50  01 

33  59 

32 

0 

-  1 

111 

50  26 

53  48 

50  14 

53  34 

47 


NEW  FORMS. 

A  somewhat  detailed  description  is  given  of  the  new  forms  fomid 
on  the  crystals.     They  may  be  grouped  as  follows: 

Groups  of  new  forms  onferberite  crystals. 

New  prisms 7 

New  positive  domes 1 

New  positive  pyramida 4 


Measurements  o/*7?{15.7.0}. 


12 


crista, 

Reflection. 

Size  of  face. 

(calculated 
68»56'). 

23 
31 

18 

Fair 

Narrow 

68    57 

Good 

Fair... 

do 

.  ..do... 

68  49 

69  14 

48 


COLORADO   FERBERITE   AND  THE   WOLFRAMITE   SERIES. 


On  crystal  23,  the  new  form,  R,  lies  between  ?{210}  and  ^{830}  as 
a  very  narrow  face,  giving  a  distinct  signal.  The  faces  measured  in 
one-haK  the  prism  zone  are  (010),  (110),  (210),  (810),  (100);  (010), 
(TlO),  (210),  (T5.7.0),  (830),  (TOO). 

On  crystal  31,  three  faces  lying  very  close  together  gave  good 
signals,  and  the  measurements  showed  the  presence  of  the  three  forms 
Z{210},i?{15.7.0},  and  C{940}. 

On  crystal  18  a  part  of  the  prism  zone  (see  description  of  6'{940}, 
crystal  18)  showed  the  forms  ^{830},  (7{940},  i?{  15.7.0},  and  Z{210}. 

In  all  the  three  occurrences  of  i?{  15.7.0}  the  form  is  associated  with 
Z{210}  and  in  two  of  them  it  Hes  between  Z{210}  and  6'{940}.  From 
these  facts,  as  well  as  the  close  agreement  in  measured  and  calculated 
values,  the  form  is  considered  as  definite  and  well  established. 

Measurements  o/*C{  940}. 


Crystal 

Reflection. 

Size  of  face. 

(calculated 
69°  51'). 

18 
31 

1 

Fair 

Narrow 

do 

Line  face 

69    49 

69  53 

70  21 

Good 

Poor 

On  crystal  18  the  form  was  one  of  three  faces  lying  close  to  Z{210} 
and  between  it  and  a{  100} .  They  form  alternating  narrow  faces,  but 
the  signals  they  gave  were  clear  and  distinct.  The  faces  were  not 
striated.  The  prism  zone  is  incomplete,  the  piece  measured  being 
only  a  fragment  of  a  crystal.  The  other  three  forms  present  in  the 
zone  are  Q{830},  i?{15.7.0},  and  Z{210}. 

On  crystal  31  the  three  forms  Z{210},  i?{  15.7.0},  and  6^(940}  he 
close  together  and  form  alternating  nonstriated  faces  similar  to  those 
observed  on  crystal  18.  The  other  parts  of  the  prism  zone  are  not 
measurable,  so  that  the  presence  on  this  crystal  of  other  faces  of  the 
last  two  forms  could  not  be  confirmed. 

On  crystal  1  the  form  was  noted  once  as  a  line  face  between  a(lOO) 
and  a  cleavage  face  of  6(010).  On  other  parts  of  the  crystal  the 
form  was  absent. 

Measurements  of  *F{  520 } . 


Crystal 

Reflection. 

Size  of  face. 

(calculated 
71°  44').- 

1 
22 

Poor 

Line  face 

do 

0        / 

71  55 
71  23 

do 

NEW   FORMS. 


49 


On  crystal  1  the  new  piism  was  noted  once  with  the  forms  a {100}, 
vi{l\0},h{QlO}.  On  crystal  22  the  portion  of  the  zone  with  the  new 
prism  was  richer  in  faces,  chose  present  being  6(010),  m(TlO),  Z(2l0), 
F(520),  a  (Too).  The  new  form  F  is  considered  as  established, 
though  the  agreement  between  the  angles  is  not  so  good  as  for  the 
two  more  complex  symbols  just  described. 


Measttrement  of  *G{720}. 


Crystal  No.  14. 


(calculated 

76»  44'). 

ye**  45^ 


The  new  prism  0  was  observed  only  once  as  a  naiTow  face  yielding 
a  fair  reflection.  It  formed  one  of  four  faces  lying  very  close  together, 
pach  of  which,  however,  gave  a  distinct  signal.  These  four  faces, 
lying  between  m(llO)  and  a(lOO),  are  G{720),  a  face  near  (410)  but 
not  determinable,  1/(510).  and  7V(1 1.2.0). 

Measurements  of  *M{510}. 


'^r 

Reflection. 

Size  of  face. 

(calculated 
80'  38'). 

13 

1 
14 

Good 

Narrow 

do 

do 

O        f 

80  21 
80  58 
80  12 

Poor 

Fair 

The  new  prism  M  is  always  associated  with  several  other  rare 
prisms.  Narrow  faces  of  it  were  found  on  crystal  13  with  n(810), 
a(lOO),  n(8T0),  J/(5T0);  on  crystal  1  as  a  striated  face  with  &(010), 
m(llO),  F(520),  a(lOO),  M(510),  Z(2T0),  m(lTO),  and  6(0T0);  and  on 
crystal  14  with  6^(720). 

Measurements  of  *iV{  11.2.0/. 


li 


^r 

Reflection. 

Size  of  face. 

(calctilated 
81»  28'). 

14 
14 

17 

Fair 

Narrow 

do 

Broad 

O       I 

81  26 
81  31 
81  48 

do 

The  two  faces  of  N  on  crystal  14  are  both  narrow  and  both  occurred 
with  other  prisms,  but  each  with  different  forms.  With  one  of  them 
the  associated  forms  were  m(TlO),  O{720),  a  face  near  (410).  3/(510), 
iV(TT.2.0)  and  cp(TOO);  with  the  other  the  forms  were  n(8T0),  i(7T0), 
and  iV(TT.2.0).  On  crystal  17  N  occurred  with  a(lOO),  n{SlO),  and 
Z(210),  being  broader  than  either  Z  or  n. 
35659°— Bull.  583—14 4 


50 


COLORADO   FERBERITE   AND   THE    WOLFRAMITE   SERIES. 

Measurements  of  *L  { 7 10 } . 


Crystal 

Reflection. 

Size  of  face. 

4> 

(calculated 

83°  16'). 

14 
5 
5 

Fair . 

Narrow 

Broad 

.do.. 

83  19 
83  11 

82  55 

Poor 

Fair 

The  occurrence  of  Z{710}  on  crystal  14  has  already  been  noted 
under  A'{  11.2.0}.  On  crystal  5  it  is  present  twice  as  broad  faces,  in 
each  case  unaccompanied  by  other  rare  prisms  and  forming  the  only 
face  between  a(lOO)  and  Z(210). 

Measurements  of  *H {904}. 


Crystal 

Reflection. 

Size  of  face. 

(calculated 
67°  07'). 

13 
14 
24 
15 
16 
19 
28 
31 
26 
34 
20 
27 

Poor 

Line  face 

do 

do 

67  06 
67  13 
67  38 
o66 
o67 
a  66 
a  69 
0  68 
(^) 
("> 
(«-) 
(b) 

do........ 

do 

No  reflection . . 

do 

do 

...do 

do 

do 

do 

do 

do 

do 

do 

do 

do 

do 

a  Approximate. 


b  Not  measured. 


This  new  dome,  always  present  as  a  hne  face,  was  noted  on  12 
crystals,  as  shown  in  the  table.  The  reflections  from  the  faces  were 
either  very  poor  or  not  discernible,  so  that  the  approximate  measure- 
ments (expressed  only  in  degrees)  were  made  by  using  the  position 
of  maximum  illumination.  The  form  is  near  to  the  simpler  one 
{201},  but  the  measurements  show  that  {904}  are  the  correct  symbols. 
The  calculated  p  angle  for  the  form  {201}  is  64°  37'. 

Figures  25,  26,  29,  30,  33,  and  34  show  the  new  form  H{904}. 

Measurements  o/  *5  {123}. 


Crystal 

Reflection. 

Size  of  face. 

(calculated 
31°  47'). 

(calculated 
34°  12'). 

13 
19 

Poor 

Small 

31  22 
30  58 

0         / 

34  21 
34  05 

do 

Line  face 

On  crystal  13  the  small  face  of  B  gave  a  poor  but  distinct  reflection. 
The  occurrence  is  illustrated  in  figure  25  (p.  66),  an  ideal  representa- 


NEW   FORMS. 


61 


tion  of  the  crystal,  wliich  shows  two  faces  of  the  form.     The  second 

side  of  the  crystal  is,  however,  not  present,  as  a  cleavage  face  of  (OTO) 

terminatos  that  side  of  the  crystal.     On  crystal  19  the  form  5(123} 

is  represented  by  a  line  face  lying  between  £'{5.9.14}  and /{Oil}, 

both  of  which  are  larger  than  B,    This  occurrence  is  represented  in 

figm'e  29  (p.  67).     Tlie  form  is  probably  also  present  on  crystal  20, 

where  a  nonmeasurable  Hne  face  was  observed  between  J{112}  and 

/{Oil},  though  it  could  not  be  determined  whether  the  form  was 

{123}  or  {5.9.14}. 

Measurements  of  *E{5. 9. 14). 


Cgs« 

Reflection. 

Size  of  face. 

(calculated 
34°  31'). 

(calculated 
34°  03'). 

19 
20 
27 

Poor 

Small 

e      / 

34  21 
34  20 
34  35 

o      / 

33  50 

34  02 
33  31 

do 

do 

do 

Line  face 

The  first  two  occurrences  of  £"{5.9.14}  are  small  faces,  much  wider 
than  the  usual  line  faces  and,  as  shown  in  figure  29  (p.  67),  the  face 
on  crystal  19  reaches  a  fair  size,  whereas  the  corresponding  simpler 
form  B{12S}  is  present  as  a  line  face.  On  crystal  20  (fig.  30,  p.  68) 
the  small  face  of  £{5.9.14}  lies  between  J{112}  and /{Oil}  and  also 
attains  an  appreciable  size.  On  crystal  27,  however,  it  is  present  as 
a  mere  line  face. 

The  symbols  for  the  form  E  are  rather  complex  and  unusual,  but 
the  identification  of  the  form  on  three  crystals,  the  small  distinct 
faces,  and  the  close  agreement  between  measured  and  calculated 
angles  show  that  the  form  is  well  established. 

Measurements  of  *A  { 337 } . 


Cr^U. 

Reflection. 

Size  of  face. 

(calculated 
50°  58'). 

(calculated 
30°  31'). 

13 
15 
20 
21 

Poor 

Line  face 

.do 

50  47 

51  00 
51  00 
50  13 

0         / 

31  08 
30  12 

30  05 

31  03 

do 

do 

do 

do 

do 

The  form  A  is  characteristically  a  line  face  between  c{001}  and 
J{112}.  The  only  forms  in  this  zone  observed  on  these  crystals  are 
m{110},  6;{111},  J{112},  ^{337},  c{001},  e{112},  and  o{Tll}.  The 
form  is  shown  in  figiu-es  25  and  30  (pp.  66,  68). 

*Z>{313}.  Only  one  face  of  this  new  form  was  observed,  this 
being  on  crystal  19,  where  a  small  face  yielded  a  fair  reflection 
whose  measurement  gave  <^,  74°  21'  (calculated  74°  44');  p,  47°  21' 
(calculated  47°  38').     The  form  is  shown  in  figure  29  (p.  67), 


52  COLORADO   FEKBERITE   AND  THE   WOLFRAMITE   SERIES. 

FORMS  PREVIOUSLY  DESCRIBED. 
COMMON   FORMS. 

The  common  forms  merit  only  a  brief  description,  as  their  relative 
development  and  occurrence  can  well  be  seen  by  studying  the  draw- 
ings illustrating  the  different  combinations  and  habits. 

In  the  prism  zone  the  orthopinacoid  a{100}  is  always  strongly 
striated  vertically.  These  striations  are  not  shown  in  the  crystal 
drawings.  The  orthopinacoid  is  often  replaced  by  vicinal  forms  sev- 
eral degrees  from  the  true  position  of  a{100}.  On  other  crystals 
the  faces  of  a  {100}  are  very  close  to  their  true  position  of  90°  00'. 
No  connection  could  be  traced  between  the  presence  of  vicinal  forms 
replacing  a{100}  and  the  presence  of  new  or  rare  prisms,  as  the 
following  table  shows : 

Measurements  of  a {100}  and  list  of  associated  prisms. 


Crystal 

^ 

Remarks. 

1 

o 

f90 
\90 

06 
55 

}{120>,{940},  {520},  ■{510>  present. 

3 

86 

00 

No  new  or  rare  prisms  present. 

4 

86 

57 

Do. 

5 

07 

•{810>,  {710}  present. 
{710}  present. 

47 

7 

f87 
188 

02 
35 

|No  new  or  rare  prisms  present. 

8 

87 

38 

Do. 

10 

{^ 

06 
11 

}       Do. 

13 

89 

53 

{810},  {510}  present. 

{720},    {510},    {11.2.0},    {810},  {710} 

present. 
{810},  {520}  present. 
{810},  { 15.7.0},  {830}  present. 
{810}  only  rare  prism  present. 

14 

90 

49 

22 
23 

86 

88 

49 
15 

32 

89 

30 

34 

r88 
\88 

24 
22 

>No  new  or  rare  prisms  present. 

35 

i86 

26 
45 

}       Do. 

The  common  prisms  Z{210}  and  m{110}  are  striated  on  some 
crystals  and  free  from  any  striae  on  others,  those  without  striae 
yielding  good  and  distinct  reflections. 

The  base  c{001}  is  generally  rounded  in  the  zone  {001}: {100}, 
commonly  giving  several  reflections,  the  extreme  ones  on  some  crys- 
tals being  several  degrees  apart. 

The  faces  of  /{Oil},  generally  small,  all  gave  good  and  distinct 
signals;  those  of  ^{102}  were  generally  distinct,  although  on  a  few 
crystals  they  were  somewhat  blurred. 

The  pyramids  are  generally  so  small  that  the  reflections  from  their 
faces  are  faint.  The  striations  on  J  {112}  cause  the  large  faces  of 
this  form  to  yield  indistinct  and  blurred  signals.  The  striations  are 
shown  in  figure  28  (p.  67). 


FORMS   PREVIOUSLY  DESCRIBED. 


53 


RARE   FORMS. 

A  number  of  rare  forms  which  were  observed  on  these  crystals 
are  entitled  to  a  short  discussion.  The  results  are  also  applied  to 
the  tabulation  of  the  forms  of  the  wolframite  group  as  developed  on 
a  later  page. 

r{120},  already  noted  by  Descloizeaux  and  Jeremejew/  is  probably 
present  as  a  line  face  on  crystal  1;  ^  measured  33°  49'  (calculated 
31°  12'). 

Q{830},  found  by  Penfield  on  hubnerite  from  Colorado,^  is  verified 
by  the  presence  of  two  line  faces  on  the  crystals  herein  described. 
On  crystal  18  a  line  face  yielded  a  fair  reflection  whose  measurement 
gave  (j)  a  value  of  73°  06'  (calculated  72°  48');  crystal  23  showed  a 
very  narrow  face,  the  measurement  of  whose  reflection  gave  <^  a 
value  of  73°  32'  (calculated  72°  48').  Penfield's^  letter  q  was 
changed  ^  to  Q,  as  q  had  already  been  preempted  by  the  form  {103}. 

d{3l0},  noted  by  Krenner,  Boggild,  and  as  doubtfully  present 
by  Moses,  was  found  once  on  crystal  9  as  a  very  narrow  face,  giving 
a  poor  reflection.  <^  measured  74°  47'  (calculated  74°  37').  The 
occurrence  is  illustrated  in  figure  24  (p.  66). 

7 {6 10}  was  first  described  by  Boggild,  who  assigned  to  the  new 
form  the  letter  p.  As  this  letter  had  been  used  by  Moses  to  desig- 
nate the  form  {214},  I  have  changed  Boggild's  p  to  j,  as  here  given. 
The  form  was  noted  once,  on  crystal  9,  as  a  medium-sized  striated 
face;  ^  measured  about  82°  (calculated  82°  10').  The  form  is  shown 
in  figure  27  (p.  67). 

71  {8 10},  first  noted  by  Groth  and  Arzruni,  has  been  observed  a 
number  of  times  on  these  crystals.  Some  occurrences  are  shown  in 
figures  22,  25,  and  27.     The  angles  measured  are  as  follows: 

Measurements  o/  n { 810 } . 


C^SU. 

Reflection. 

Size  of  face. 

(calculated 
84"  06'). 

14 
17 
32 

Fair 

84  13 

83  50 

84  23 
84  52 
84  20 

do 

do 

do 

.do.   . . 

Narrow  and  striated 

Narrow . 

do 

Narrow  and  striated 

'^{104},  observed  only  by  Jeremejew,  is  confirmed  by  finding  it  on 
crystal  13  as  a  Mne  face  with  t(l02)  and  77(904),  as  shown  in  figure  25 
(p.  66).  The  reflection  was  very  poor  and  its  measurement  gave  p 
16°  28'  (calculated  15°  08'). 


»  See  Bibliography,  pp.  74-75,  for  references. 
*  Dana's  System  of  mineralogy,  6th  ed.,  p.  982. 
«  Goldschmidt's  Winkeltabellen,  p.  366, 1897. 


54 


COLOKADO  FERBERITE  AND  THE   WOLFRAMITE   SERIES. 


/•{1. 0.11},  the  only  negative  dome  observed  on  any  of  these  crystals, 
was  first  noted  by  Groth  and  Arzruni  and  is  verified  by  finding  it 
on  three  of  these  crystals.  The  reflections  were,  however,  very  poor, 
owing  to  the  rounded  and  striated  character  of  the  faces.  For  com- 
parison the  original  measurement  of  Groth  and  Arzruni  is  added  to  the 
table  below.  The  p  angle,  as  here  given,  is  equal  to  (001  aT.0.11)  — 
(90°-/3)[  =  0°  28'].  The  calculated  values  of  p  for  {T.0.10}  and 
{1.0.12}  are  also  added,  and  though  my  own  measurements  would 
agree  better  with  these  two  forms,  it  is  preferable,  on  account  of  the 
poor  quality  of  the  reflections,  to  assign  them  to  the  known  form 
HT.O.U}. 

Measurements  of  y [1.0. 11). 


Crystal 

Reflection. 

Size  of  face. 

p 

(calculated 

4°  59'). 

6 

9 

35 

Poor. . 

Line  face 

do 

do 

3  51 
5  23 
3  46 

do 

do 

As  measured  by  Groth  and  Arzruni,  p=4°  59J'. 
p  calculated  for  <1.0.10>=5''  32'. 
p  calculated  for  {1.0.12>=4°  32'. 

The  form  r{T.OAl)  is  illustrated  in  figures  23  and  24  (p.  66). 

2) {2 14}  was  first  described  by  Moses  on  a  crystal  from  Boulder 
Coimty,  Colo.  It  was  also  noticed  by  me  as  narrow  faces  on  crystals 
19,  29,  and  30  (see figs.  19  and  29,  pp.  64,  67),  l}dng  in  the  zone  c(OOl) : 
Z(210).  The  faces  gave  poor  reflections.  The  angles  measured  by 
Moses  are  also  shown  in  the  table  below. 

The  form  was  measured  on  crystal  19  with  the  following  result: 

Measurements  of  p{ 214 } . 


Angle. 

Calculated. 

Measured. 

Schaller. 

Moses. 

^ 

p 

67  53 
29  55 

69  42 
31  22 

68  46 
30  17 

In  addition  to  the  measurements  of  2>{214}  given  above,  the  form 
was  identified  on  crystals  29  and  30.  These  crystals,  however,  were 
so  incompletely  developed  that  they  could  not  be  well  placed  in 
polar  position.  The  angle  between  p(214)  and  Z(210)  was  therefore 
measured,  with  the  following  results: 

Measurements  of  angle  p(214):  Z(210). 

Crystal  29 58    39 

Crystal  30 60    05 

Calculated 60    05 


DISCUSSION  OP  THE  PRISM  ZONE.  55 

On  all  three  of  these  crystals  the  form  occurred  in  the  zone  c(OOl) : 
Z(210),  and  on  crystal  19  it  was  also  determined  to  lie  in  the  zone  of 
and  between  ^(102)  and  J (112),  so  that  its  determination  as  (214)  is 
verified  by  its  zonal  relations. 

DISCUSSION    OF    THE    PRISM    ZONE. 

The  prism  zone  contains  numerous  forms  of  somewhat  complex 
symbols  and  a  discussion  *  of  these  forms  is  here  given  in  order  to 
show  how  closely  the  forms  approach  the  normal  series. 

The  entire  prism  zone  from  &(010)  to  a(lOO)  shows,  when  plotted 
in  gnomonic  projection  (see  fig.  35,  p.  70),  a  partition  into  three  parts, 
the  points  of  division  being  m(llO)  and  d(S10).  The  three  zone 
segments  are  then: 

(1)  6(010),  r(120),  S{7.11.0),  m(llO). 

(2)  7n(110),  /(210),  i2(15.7.0),  C(940),  jF'(520),  Q(830),  rf(310). 

(3)  d(310),  (?(720),  if(510),  N{11.2.0),  ;(610),  L(710),  n(810),  a(.100). 

In  the  following  discussion,  these  three  segments  are  taken  up  in 

turn: 

(1)  Zone  segment  b m. 

J.  {  h  r  S  m 

^'^^ lOlO        120        7.11.0        110 

Symbol=^ ^2  ll  ^ 

V  7 


N^ 


7 
In  place  of  r  or  (7.11.0),  the  simple  form  2  or  (230)  should  occur. 

The  form  /S (7. 11.0)  was  not  observed  by  me  but  was  described  by 
Warren.  The  measured  angle  (7.11.0)  :  (7.11.0)  is  given  as  74°  51', 
whereas  the  calciilated  angle  (230)  :  (230)  is  77°  50',  a  difference  too 
great  to  allow  of  the  form  being  referred  to  the  symbol  (230).  Com- 
pare also  the  remarks  on  page  69  on  the  indices  of  this  form. 


Form. 


(2)  Zone  segment  m d. 

(  m 
"\U0 


I  R  C  F  Q  d 

210        15.7.0        940  520        830        310 


h  1  9  15  ?  5  8 

Symbol=^ i  J  7  4  2  3 


-1. 


8  5  3  5 

7  4  2  3 


-JL 0  1  1  § 

2-v  3  3 


i-l. 


1  2 

3  3 

1  12,3 

3  2      3  2 


>  For  a  description  of  the  methods  of  the  discussion,  see  Hillebrand,  W.  F.,  and  Schaller,  W,  T.,  The 
mercury  minerals  from  Terlingua,  Tex.:  U.  S.  Geol,  Survey  Bull.  405,  p.  13, 1909. 


56  COLORADO   FERBERITE  AND  THE  WOLFRAMITE   SERIES. 

The  forms  fit  well  into  the  normal  series  notwithstanding  their 
complex  indices. 

(3)  Zone  segment  d a. 

Fonn  I  ^         ^         ^^  ^~  J  L         n  a 
1310       720       510       1L2.0       610-     710       810       100 

Symbol=| 3^5  y  6  7  8  oo 

1  5 

^^-3 0  2  ^  2  34500 

v-2 0  2  1  2  3  00 

AT  /v         1      1      2  T      3 

^3 - 0       3     2     3^22 

All  the  new  prisms  fit  well  into  the  normal  series. 

HABIT.  _^. 

J'ive  very  distinct  habits  were  observed  on  the  crystals  examined, 
babit  meanmg  the  relative  development  and  size  of  the  different 
crystal  faces  and  the  consequent  resultant  shape  of  the  crystal  as 
a  whole.  Thus  twin  crystals  are  not  considered  as  necessarily  of 
different  habit  from  a  simple  untwinned  crystal.  These  G^re  habits 
are  as  follows: 

1.  Long,  narrow,  wedge-shaped.  This  is  the  habit  most  frequently 
observed  for  the  ferberite  crystals  studied.  This  is  the  habit  of  the 
penetration  twins  (figs.  17  and  18,  p.  64)  but  not  of  the  contact  twins. 
(See  Pis.  VII  and  VIII,  A,  pp.  18,  19,  and  fig.  3.) 

2.  Short,  prismatic,  somewhat  flattened  parallel  to  the  ortho- 
pmacoid  a  {100}.  Crystals  of  this  habit  are  fairly  abundant.  (See 
Pis.  IX,  p.  20,  and  X,  p.  21,  and  fig.  4.) 

_3.  Tabular,  parallel  to  a{100}.     Rarely  observed  in  simple  crystals 
but  the  common  habit  for  the  individuals  of  a  contact  twin.      (See 
fig.  5,  also  the  twin  crystals  shown  in  figs.  14  and  15,  p.  63.) 
.  4.  Cubic...j:are.     (See  PI.  VIII,  B,  p.  19,  and  fig.  C.) 

5^ Rhombic,  fairly  abundant.  (See  Pis.  XI,  p.  22,  and  XII,  p.  23, 
and  fig.  7.) 

Besides  the  habits  mentioned  above,  two  forms  were  noted  which 
owe  their  shape  to  the  cleavage  of  the  crystals  and  are  therefore  not 
habits  of  the  mineral.  The  first  of  these  forms  occurs  in  thin  plates, 
which,  as  can  be  seen  by  reference  to  figure  8,  A  (p.  58),  owe  their 
tabular  appearance  to  the  &{010}  cleavage.  The  complete  crystal 
from  which  this  thin  plate  was  cleaved  was  probably  of  the  fourth  or 
cubic  habit.  The  second  form  occurs  in  long,  slender  rods  and  like- 
wise owes  its  peculiarity  of  form  to  cleavage.  As  illustrated  in  figure 
8,  B,  it  is  probably  derived  from  the  edge  of  a  crystal  of  habit  1  (see 
figs.  3  and  9),  where  the  prism  Z{210}  extended  to  the  edge  of  the 
crystal. 


HABIT. 


67 


Habit  1.  The  wedge-shaped  crystals  are  generally  striated  in  the 
prism  zone  with  the  forms  a{100},  Z{210},  and  m{110}  grading  into 
one  another,  as  shown  in  figure  9.  On  many  crystals,  however,  the 
individual  prism  faces  are  sharply  separated  and  commonly  yield  single 


X 


FiGTTRE  3.— Long,  narrow,  wedge-shaped  crystal  of  habit  1,  the  most  frequently  observed  habit.    Forms: 

c{001},  «{100>,  7n{nO}.  ?{210}. 


I 


<c 


b 

i-m 


F^GUKE  4.— Short,  prismatic,  somewhat  flattened 
crystal  of  habit  2.  Fairly  abimdant.  Forms: 
c<001>,  6{010>,  a{100>,  77i{110>,  Z{210>,/{011>. 


FiGUEE  5.— Tabular  crystal  of  habit  3.  Common 
habit  for  contact  twins,  but  rare  for  single  crys- 
tals. Forms:  c{001},  6{010},  a{100},  7n{110}, 
Z{210>. 


Figure  6.— Cubic  crystal  of  habit  4.   Rare.   Form.s: 
c{001>,  6{010>,  a{100>,  <{102>. 


Figure  7.— Rhombic  crystal  of  habit  5.    Fairly 
abundant.    Forms:  b{010},  a{100>,  /{ 102>. 


distinct  reflections.  Figure  10  (crystal  4)  also  represents  a  tj'pical 
crystal  of  this  habit.  On  removing  these  crystals  from  the  matrix, 
to  which  they  are  firmly  attached,  they  usually  cleave,  and  the  result- 
ing loosened  crystal  piece  will  consequently  be  much  shorter  in  the 


58 


COLORADO  FEBBERITE  AKD  THE  WOLFRAMITE  SERIES. 


H 


direction  of  the  h  axis  than  the  original  crystal.  From  the  sharp  edge 
on  one  side  such  cleaved  pieces  show  a  peculiar  axlike  shape.  (See 
fig.  11,  crystal  2.)  The  penetration  twins  (figs.  17, 18,  p.  64,  and  PL  VIII, 
A,  p.  19)  are  generally  of  this  habit,  and  the  contact  twins  (figs.  14 
and  15,  p.  63)  are  of  the  tabular  or  third  habit.  The  wedge-shaped 
crystals  of  this  first  habit  are  generally  poor  in  forms,  few  being 
found  except  the  common  ones,  a{100},  c{001},  Z{210},  m{110}, 
&{010},/{011}. 

Habit  2.  The  short  prismatic  habit,  somewhat  flattened  parallel  to 
a{100},  is  the  common  habit  for  the  wolframite  group  in  general  and 
is  fairly  abundant  on  the  Colorado  ferberite.  An  example  was  shown 
in  figure  4  (crystal  1),  and  figure  12  illustrates  the  same  combination 
as  shown  in  figure  4,  but  with  a  habit  intermediate  between  the  first 

or  wedge  shaped  and  the  second  or 
short  prismatic .  The  two  habits  show 
all  gradations,  and  it  is  impossible  to 
refer  some  crystals  to  one  of  these  two 
habits  rather  than  to  the  other.  Fig- 
ure 12  does  not  illustrate  any  partic- 
ular crystal  measured,  but  many  were 
seen  having  about  the  relative  pro- 
portions shown  in  the  figure. 

Habit  3.  The  tabular  habit  may  be 
considered  as  a  further  development 
of  the  change  from  habit  1  to  habit 
2,  which  is  intermediate  between 
habits  1  and  3.  Single  crystals  of 
this  habit,  as  shown  in  figure  5,  are 
rare,  but  in  contact  twins  they  are 
fairly  abundant.  The  orthopina- 
coid,  a{100}-,  is  strongly  striated  in 
the  twin  crystals  of  this  habit,  whereas 
the  other  forms  in  the  prism  zone 
are  in  general  nearly  free  of  strise. 

Habit  4.  The  cubic  crystals  were  found  abundantly  on  one  specimen, 
aside  of  which  was  literally  covered  with  them  (PI.  VIII,  B,  p.  19,  and 
fig.  6).  They  were  small,  few  being  over  a  millimeter  in  length,  and  were 
highly  iridescent.  Some  of  the  crystals  are  slightly  elongated  in  the  ver- 
tical direction,  whereas  others  are  nearly  perfectly  cubic.  The  shape  of 
the  crystals  is  conditioned  by  the  combination  being  essentially  that 
of  the  three  pinacoids,  a{100},  &{010},  c{001},  two  of  which  are  at 
right  angles  to  each  other,  and  the  third  very  nearly  so,  the  angle 
being  89°  32'.  The  dome  ^{102}  is  always  present,  and  the  pyramid 
i { 1 12 }  is  usually  developed.  The  crystals  of  this  habit  are  very  poor 
in  forms. 


B 


Figure  8.— Cleavage  pieces  of  crystals.  A, 
thin  tabular;  B,  long,  prismatic.  Forms: 
c{001>,  6{010}  cleavage,  a{100>,  1{210}. 


HABIT. 


59 


FiouEK  9.— Striations  on  wedge-shaped  crystals  of  habit  1,  causing  a  rounded  appearance  in  the  prism 
zone.    The  top  base  is  also  slightly  striated  and  in  some  crystals  rounded. 


FiQUKti  10.— Crystal  4,  wedge-shaped  habit,  which  has  sharp,  distinct  faces,  not  rounded  as  in  figure  9. 
Forms:  c{001>,  6{010>,  c{100>,  7n{110>,  i{210>,/{011>. 


Figure  11.— Peculiar  shape  of  crystals  of  wedge-shaped  habit  caused  by  cleavage  on  6{010}.    Crystal  No.  2. 
Forms:  c<001>,  6{010>,  m{no},  /{210>,/{011}. 


Figure  12.— Crystal  of  a  short  prismatic,  somewhat       Figure  13.— Crystal  of  rhombic  habit,  nearly  equi- 


flattened   habit.     Forms:  c{C01>,  fe{010>,  a{lOO}, 
wi{110>,  Z{210>,/{011>. 


dimensional.     Compare    with    figure  7,   p.  57. 
Crystal  No.  24.    Forms:  &{010>,  o<100>,  t{  102>. 


60 


COLOEADO  FERBEMTE  AND  THE   WOLFRAMITE   SERIES. 


Habit  5.  The  rhombic  crystals  are  very  abundant  on  some  specimens 
and  other  habits  are  then  entirely  absent.  (See  Pis.  XI  and  XII.) 
The  rhomboids  consist  of  either  a  single  crystal  bounded  by  plane  sur- 
faces or  of  an  agglomeration  of  innumerable  crystals,  each  deviating  a 
little  more  from  strict  parallelism  with  the  first  unit.  The  crystals  are 
generally  elongated  parallel  to  the  c  axis,  as  shown  in  figure  7,  though 
some  of  them  are  more  nearly  equidimensional,  as  shown  in  figure  13 
(crystal  No.  24).  The  characteristic  combination  is  6{010},  a{100}, 
^{102},  and  other  forms  are  rare.  Many  of  these  rhombic  crystals  are 
fairly  large,  the  longer  diameter  of  .^{102}  in  average  individuals  meas- 
uring nearly  half  a  centimeter. 

COMBINATIONS. 

The  combinations  observed  on  the  38  crystals  measured  are  shown 
in  the  following  tables,  wherein  the  different  crystals  have  been 
grouped  according  to  their  habit,  as  the  various  habits  have  a  mark- 
edly different  combination.  Thus  the  essential  forms,  that  is,  those 
which  are  characteristic  for  a  certain  habit,  are  given  below  for  the  five 
different  habits  observed.  The  forms  are  further  grouped  as  promi- 
nent or  not  prominent,  depending  on  whether  or  not  they  have  a 
decided  influence  on  the  shape  of  the  crystal.  Forms  that  are  not 
prominent  are  placed  in  parentheses. 

Characteristic  forms  for  each  crystal  habit. 


Form. 

^s^er 

2.  Short 
pris- 
matic. 

3.  Tabu- 
lar. 

4.  Cubic. 

5.  Rhom- 
bic. 

c<001 
iKOlO 
a<100 

m\m 

1{210 

mn 

dm 

a»{lll 

^ 

c 

(&) 
a 
,   m 
I 
f 

c 
6 

a 
(m) 

(/) 

(0 

a 

(771) 

c 
6 
a 

f: . 

b 
a 

k 

[::::::::;:; 

>. 

(I) 

(t) 

t 

t . 

... 

U) 

U) 

::.:::::::: 

Combinations  on 

crystals  with  wedge-shaped 

habit 

Form. 

Crystal  No. 

■ 
2 

4 

8 

29 

30 

31 

32 

33 

34 

35 

c{001 

\ 

c 
b 

a 
m 
I 

c 
6 
a 
m 

I 

c 
b 
a 
m 
I 

c 
6 
a 
m 
I 

c 
b 
a 
m 
I 

c 
b 
a 
m 
I 

R 
C 

c 
b 
a 
m 
I 

c 
b 
a 
m 
I 

c 
6 
a 
w, 
I 

c 
6 
a 
m 
I 

WOIO 
aUOO 

mhlO 
H210 

i2<15.7 

[. 

|. 

[ 

.b> 

C{940 

l^. 

1 

7l{810 

} 

1 

n 
f 

MOll 

/ 

f 

f 

f 

'h 

f 
"'r"\ 

H|904 

H 

rh.O. 

6><111 

liv 

^.! 

to 

(0 

0) 

0) 

CD 

p|214 

|. 

V 

V 

o|lll 

\. 

J 

A 

0 

\. 

0 

'  1 

COMBINATIONS. 
Combinations  on  crystals  with  short  prismatic  habit. 


61 


Form. 

Crystal  No. 

1 

3 

5 

6 

7 

0 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

c<001  

c 
b 
a 
m 

I 

r 

c 
h 
a 
m 
I 
r 

e 
b 
a 
m 
I 
r 

c 
b 
a 
m 

I 

T 

c 
b 
a 
m 
I 
r 

c 
b 
a 
m 

I 

r 

c 
b 
a 

TO 

/ 

r 

c 
b 
a 

TO 

I 

c 
b 
a 

TO 

I 

c 
b 
a 

TO 

c 
b 
a 

TO 

I 

c 
6 
a 

TO 

I 

c 
b 
a 

TO 

c 
b 
a 

TO 

I 

e 
h 

! 

woio  

0  100 

m  110> 

TO  1  rh 

I  1   { 

/{210> 

rh20  

i?{15.7.0> 

R 
C 

C  940V 

C 
F 

i 

F  520> 

p 

Q{830  

Q 

a{310> 

d 

0  720> 

G 
M 

N 

Jlf{510         

M 

M 

■ 

JV{11.2.0> 

1 

.... 

.... 

N 
J 

j/610> 

^ 

1 

L/710V 

:::j  :; 

• 

L 
n 

n|810> 

...^. ........ 

n 

/ 
u 
t 
H 

n 

f 

/loiiy 

f 

f 

/ 

/ 

f 

f 

.... 

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/ 

f 

/ 

/ 

ti{104i 

t  102> 

t 

t 
H 

t 
H 

t 
H 

t 

t 

t 
H 

t 
H 

t 

t 

H  904 

Jl.o.iii 

r 

r 

' 

B  123>           

B 

B 
E 

ill 
A 

£}5.9.14> 

E 

0) 

A 
A 

E 

"a 

A 

at 
A 

^J\\\     

(0 

a 

J 
A 

"a' 

w 
J 
A 

w 
A 

A  112  > 

A 

A 

A  337> 

p  214>               ..   . 

I 

B  313i 

«.  121 

s 

e-  Tl2> 

e 

0 

0.  In  

0 

0 

0 

0 

1 

Combinations  on  crystals  with  tabular  habit. 


Form. 

Crystal  No. 

10 

11 

12 

23 

27 

28 

c{001> 

c 
b 
a 

TO 

I 

c 
6 
a 

TO 

c 
b 
a 

TO 

R 

Q 

n 

c 
a 

c 
6 
a 

WOIO} 

a\  lOOV           .     . 

7n-|ll0> 

l  210>      

R{\b  7  0> 

Q  830V  

tJsioV      

/  011/ 

f 

/ 

t  102>  

< 

H 
E 

t 
H 

R  904  .             .  . 

E.  5.9.14> 

Combinations  on  crystals  with  cubic  and  rhombic  habits. 


Cubic  habit. 

Rhombic  habit. 

Foim. 

Crystal  No. 

Crystal  No. 

38 

37 

38 

24 

25 

26 

c{001, 
WOIO^ 
ahoo 
i{210 
«102 
fl{904 
A{112 

c 
b 
a 

c 
6 
a 

c 

b 

a 

...... 

H 

f 

b 
a 

I 
t 
H 

6 

a 
I 
t 
H 

[■• 

t 

t 

A 

A 

62  COLORADO  FEKBEEITE   AND   THE   WOLFRAMITE   SERIES. 

TWINNING. 

Twin  crystals  were  often  observed.  Only  one  twinning  law  was 
noticed,  namely,  with  {023}  as  the  twinning  plane.  The  many 
groupings  parallel  to  a{100}  were  carefully  examined  for  evidences 
of  twinning  on  the  a(lOO)  face,  but  none  were  seen.  As  these  parallel 
groupings  generally  have  the  i (102)  face  well  developed,  twinning  on 
the  a  (100)  face  would  cause  a  twinned  face  of  ^(102)  to  assume  the 
position  of  (T02),  and  there  would  then  be  an  apparent  rear  orthodome 
as  well  as  a  front  one  on  such  a  twinned  crystal.  The  absence  of  such 
a  rear  orthodome  would  indicate  that  these  parallel  groupings  were 
not  twinned. 

Though  only  one  twinning  law  was  observed,  namely  {023},  there 
were  two  kinds  of  twins  according  to  this  law,  namely,  contact  and 
penetration  twins.  Both  were  observed  many  times,  though  the 
contact  twins  are  more  abundant. 

The  contact  twins  are  illustrated  in  figures  14  and  15,  which  show 
the  twinned  crystal  facing  in  two  directions,  or  in  other  words  show 
the  two  positions  a  twinned  group  will  take  according  to  which  face 
of  {023}  acts  as  twinning  plane.  Both  positions  of  the  twinned  group 
have  the  same  crystallographic  relationship.  The  position  shown  in 
figure  14  shows  the  cHnopinacoid  h{010]  of  the  twinned  crystal  adjoin- 
ing the  same  form  of  the  untwinned  crystal.  In  figure  15  the  basal 
pinacoid  c{001}  of  the  twinned  crystal  is  shown.  In  the  two  illustra- 
tions the  relationships  of  the  contact  twins  are  more  clearly  indicated 
than  can  be  done  by  a  written  description. 

The  fine  of  contact  of  the  two  crystals  affords  some  points  of  interest, 
but  for  the  present  only  a  description  of  it  is  given.  Theoretically 
it  should  be  a  straight  line,  as  drawn  in  figures  14  and  15,  but  actually 
it  is  very  uneven,  the  two  parts  of  the  twinned  crystal  being  very 
irregularly  dovetailed,  as  illustrated  diagrammaticaUy  in  figure  16, 
which  was  drawn  from  a  twinned  crystal  (notebook  No.  A 13),  as  seen 
on  the  goniometer. 

In  the  penetration  twins  tne  containing  unit  is  always  much  larger 
than  the  one  which  is  partly  embedded  and  projects  out  of  the  middle 
of  the  larger  crystal,  as  shown  in  figure  17.  The  two  crystals,  though 
of  different  appearance,  have  the  same  combination  of  crystal  forms 
as  those  shown  in  figures  14  and  15.  Similarly  figure  18  shows  the 
same  kind  of  penetration  twin  with  the  smaller  twinned  crystal  in  the 
opposite  direction  to  that  in  figure  17.  The  large  untwinned  crystal 
in  figure  18  is  shown  with  one  end  cleaved  off,  due  to  the  clino- 
pinacoidal  cleavage  &(010).     (See  PL  VIII,  A,  p.  19.) 

The  angle  c{001) :  h(010)  (fig.  17)  is  29°  58',  and  the  angle  c(OOl): 
c(OOl)  (%.  18)  is  60°  02'.  These  angular  values  are  here  given  as 
reference  will  be  made  to  them  later  and  the  position  of  the  faces 
forming  the  angles  can  here  well  be  seen. 


TWINNING. 


63 


A  peculiarity  notod  by  Mr.  Hess  on  several  crystals  similar  to  the  one 
shown  in  figure  18  is  that  in  front  of  the  twinned  crystal,  on  the  larger 
untwinned  unit,  is  a  small  cavity  bounded  by  rough  planes  which 


Figure  14.— Contact  twin  on  (053).     Forms:  &{010>» 
o{100>,7n{110>,Z{210}. 


Figure    15,— Contact    twin  on   (023).     Forms: 
c{001},  6{010>,  a{100>,  to{110>,  ^{210}. 


Figure  16.— Line  of  contact  of  two  contact  twins. 


however  suggest  that  they  may  be  slightly  developed  terminal  faces, 
such  as /{Oil}.  (See  PI.  VIII,  A,  p.  19,  center.)  They  may  be 
caused,  however,  by  crystals  of  scheelite,  jiow  removed. 


64  COLORADO   FERBERITE   AND   THE    WOLFRAMITE   SERIES. 


Figure  17.— Penetration  twin  on  (023).    Forms:  c{001},  6{010>,  a{100>,  m{110},  Z{210>. 


Figure  18.— Penetration  twin  on  (023).    Forms:  c<001>,  &{010>,  o{100>,  m{110>,  Z{210}. 


.^ 


^' 


^f 


Figure  19.— Crystal  29,  showing  rare  form  p.        Figure  20.— Crystal    32.    Forms:   c{001  >,  6{010}, 
Forms:  c{001>,6{010},o{100>,Z{210},p{214}.  a{100>,  m{110},  ^{210},  A011>,^{112>. 


Figure  21.— Crystal  33.    Wedge-shaped  crystal  with  unequal  development  of  the  faces  of  /.    Forms: 
c{001>,  6{010},  o{100>,  m<110>,  Z{210},/{011>,  J<112>,  c^{lll}. 


COLORADO   FERBERITE   AND  THE   WOLFRAMITE   SERIES.  66 

DESCRIPTION   OF   MEASURED  CRYSTALS. 

Only  such  crystals  as  arc  illustrated  by  drawings  will  be  hero 
mentioned.  The  general  types  of  habit  have  already  been  shown 
under  the  section  entitled  ''Habit/'  where  drawings  of  a  few  of  the 
measured  crystals  were  also  introduced.  In  general  the  following 
figures  show  the  crystals  in  their  ideal  development.  As  most  of 
them  were  bounded  on  one  side  by  the  cleavage  face  (OTO)  the  exact 
dimension  of  the  crystals  in  this  direction  coidd  only  be  estimated, 
but  by  observing  similar  crystals  that  were  intact  it  is  believed  that 
the  proportions  shown  in  the  figures  closely  approximate  the  true 
relative  dimensions.  The  crystals  illustrated  will  bo  grouped  under 
the  five  habits. 

Crystal  29  (fig.  19)  is  simple  in  its  combination  but  shows  the 
rare  form  2^(214}  fairly  weU  developed.  It  is,  moreover,  except 
c{001},  the  only  terminal  form  on  this  crystal.  Crystal  No.  32  (fig. 
20)  shows  a  common  combination  for  a  number  of  minute  stout 
crystals  in  which  the  wedge  shape  is  not  so  characteristic  as  in  crystal 
No.  33  (fig.  21).  Here  also  the  upper  and  lower  faces  of /{Oil}  arc 
unequally  developed.  With  the  large  development  of  Z{210}  the 
pyramid  faces  generally  become  smaller. 

Crystal  5  (fig.  22)  is  remarkable  in  possessing  such  a  small  ortho- 
pinacoid,  a{100},  the  large  faces  of  n{810}  seeming  to  replace 
the  usually  large  faces  of  a.  Crystals  6  (fig.  23)  and  9  (fig.  24)  are 
both  shown  in  their  actual  condition,  with  one  side  bounded  by 
the  cleavage  face  (OTO).  Both  of  them  show  a  line  face  of  the  rare 
negative  dome  /-{T.O.I  1}  and  figure  24  also  shows  the  large  positive 
dome  t{102}.  The  rare  prism  (^{310}  is  shown  as  a  line  face,  and 
a  face  of  7  {610},  though  not  shown,  is  also  present.  Crystal  13 
(fig.  25)  shows  a  nimiber  of  new  and  rare  forms,  all  as  narrow  faces, 
generally  mere  line  faces,  except  one  form  which  is  present  as  a 
minute  equidimensional  face.  The  new  forms  7/{904},  J.  {337}, 
J5{123},  and  the  rare  forms  n{8l0}  and  u{104}  are  the  ones  referr^ 
to.  The  clinodome,  /{Oil},  is  much  narrower  and  longer  than 
is  usual  for  the  faces  of  tliis  form.  Crystal  16  (fig.  26)  gives  a 
combination  seen  on  numerous  crystals  not  measured.  The  new 
form  //{904}  is  generally  present  on  such  crystals.  Crystal  17 
(fig.  27)  shows  y*{610},  7i{810},  and  o{Tll}  besides  the  more  common 
forms.  Crystal  18  (fig.  28)  shows  the  striations  observed  on  i{112}, 
these  strise  being  parallel  to  the  intersection  edges  (112)  :  (001) 
and  (112)  :  (210),  respectively.  The  crystal  is  also  more  elongated 
in  a  vertical  direction  than  is  usual.  Crystal  19  (fig.  29)  shows 
a  number  of  new  pyramids,  namely,  i>{313},  ^{123},  £"(5.9.14}, 
and  the  rare  pyramid  p{214}.  The  zonal  relationships  of  J  (112), 
£(5.9.14),  jB(123),  /(Oil),  and  m'(TlO)  could  be  well  seen  on  this 
crystal.  Crystal  20  (fig.  30)  also  shows  the  new  form  £{5.9.14},  as 
well  as  ^{337}  and  /7{904}. 
35659°~Bull.  583—14 5 


66 


COLORADO   FERBERITE   AND   THE   WOLFRAMITE   SERIES. 


-=^=P^^ 


Figure  22. — Crystal  5,  remarkable  for  its  small         Figure  23.— Crystal  G,  with  rare  form  y.   Forms: 
orthopinacoid  c{100}.    Forms:  c{100},  6<010},  c{001>,  fc{010>,  g{100},  m-{110>,  Z<210},  /{Oil}, 

c{l(X)},  to{110>,  i{210>,  n{ 810}, /{Oil}.  r{1.0.11},  u){\\\^. 


4       I 


FioUBE  24.— Crystal  9,  with  rare  forms  r  and  d.    Forms:  c{001},  6{010},  o{100},  to{110>,  Z{210},  d{310}, 
/{Oil},  t{\Q2},  r{T.0.11}.    The  form  ;{610},  not  shown  in  the  figure,  is  also  present  on  this  crystal. 


Figure  25.— Crystal  13,  showing  the  new  forms  A,B,  and  77 and  the  rare  forms  n  and  u.    Forms:  c{00l}, 
&{010},  o{100},  7n{110},  ^{210},  n{ 810}, /{Oil},  «{104},  t\\Q2},  ir{g04},  ^{337},  ^{112},  w{lll},  .B{123}. 


MEASURED  CRYSTALS. 


67 


Crystal  36  (fig.  31)  shows  a  cubic  crystal  somewhat  elongated 
in  the  vertical  direction.  The  form  /{102}  is  invariably  present  on 
these  crystals,  as  is  also  generally  i{112}.     Figure  32  illustrates  a 

4- 


'& 


FiQUKE  26.— Crystal  16,  a  combination  observed  on  FiGxmE  27.— Crystal  17,  showing  rare  forms 
many  crystals  not  measured.  Forms:  c{001},6{010>,  n,  j,  and  o.  Forms:  c{001},  6{010>,  a{100>, 
a-llOO},  to{110},  /{210>,  K102>,  .ff<904>,  J<112>,  6/{lll}.        7n{110},  Z{210},  i{610},  7Z<810},  <{102>,  J{112>, 

o{Ill}. 


b 


Figure  28.— Crystal  18,  show- 
ing striations  on  A.  Forms: 
c{001>,  6{010},  a{100>,  nz{110>, 
/<210},t{102>,J{112>. 


FioxJBE  29. — Crystal  19,  showing  new  forms  D,  B,  and  E. 
The  zone  J{112},  £{5.9.14>,  i?{123>,  /{Oil},  and  m'{110>  is  well 
shown.  Other  forms  are  c{001},  6{010>,  a{100},  m{\\^},  Z{210>, 
t<102>,  -^{904},  iu{  111),  p<214},  i><313}. 


cubic  crystal  apparently  slightly  elongated  in  the  direction  of  the 
a  axis,  but  in  reality  the  original  crystal  was  elongated  parallel  to 
the  &  axis,  as  the  crystal  shown  in  the  drawing  is  incomplete,  part  of 


68  COLORADO   FERBERITE   AND   THE   WOLFRAMITE    SERIES. 


FiQUBB  30.— Crystal  20,  with  new  forms  //,  A,  and  E.    Forms:  c{001},  6{010>,  o{100},  m{nQ},  f{210>, 
/{011>,^{102>,  //{904},^{337},J{112>,^111},  E{5.9.U}. 


c 

^^ 

.^^  t 

h 

1 

-^ 

1* 

a 

} 

1 

^ 

Figure  31. — Crystal  36,  a  cubic  crystal,  some- 
what elongated  parallel  to  its  vertical  axis. 
Forms:  c{001>,  6{010>,  a{100>,  f{102>,  J{112>. 


Figure  32.— Cubic  crystal  (No.  37),  apparently 
elongated  parallel  to  a  axis,  but  in  reality 
elongated  parallel  to  &  axis,  the  left-hand 
side  of  the  crystal  having  cleaved  off. 


Figure  33.— Rhombic  crystal  (No.  25), with  the 
broad  orthopinacoid  replaced  by  numerous  nar- 
row alternating  feces  of  a{  100}  and  /{  210). 


Figure  34. — Crystal  26,  a  rhombic  crystal.    Forma: 
c{001>,  6{010>,  a{100>,  t{102>,  .H{904>. 


FORM   SYSTEM  OP  THE  WOLFRAMITE   GROUP.  69 

it  having  cleaved  off.  The  face  of  <{  102}  is  much  narrower  than  that 
on  figure  31. 

Crystal  25  (fig.  33)  shows  a  rhombic  crystal  similar  to  those  shown 
in  figures  7  and  13  (pp.  57,  59),  with  the  broad  orthopinacoid  a{100}, 
replaced  by  numerous  narrow  alternating  faces  of  o{100}  and  Z{210}, 
those  of  Z{210}  being  much  narrower  than  those  of  a{100}.  The 
form  //{904}  is  also  present.  The  drawing  is,  however,  but  a  poor 
representation  of  the  true  appearance  of  the  crystal.  Crystal  No.  26 
(fig.  34)  shows  the  rhombic  combination,  a,  h,  t,  modified  by  c{001} 
and /7{  904}. 

FORM  SYSTEM  OF  THE  WOLFRAMITE  GROUP. 

CRITICAL   STUDY   OF   FORMS. 

Before  the  monoclinic  character  of  wolframite  was  determined  it 
was  considered  as  orthorhombic,  and  it  is  therefore  not  possible  to 
tell  which  are  the  negative  and  which  are  the  positive  forms  in  the 
earlier  descriptions.  The  list  of  forms  is  fairly  extensive,  a  total  of 
49  being  recorded.  Some  of  these  forms  will  be  briefly  commented 
on,  as  follows: 

iS'{ 7.11.0}  was  described  by  Warren  as  new  and  the  letter  i  assigned 
to  it.  As,  however,  i  had  already  been  preempted  by  the  form 
{403},  the  letter /S'  is  assigned  to  the  form  {7.11.0}.  The  measured 
angle  is  given  as  follows:  (7.11.0):  (7.11.0)  =74°  51'.  The  calcu- 
lated value  is  75°  16'  and  the  calculated  value  for  the  simpler  form 
{580}  is  74°  16'.  The  differences  between  the  angles  measured  and 
the  values  calculated  are,  for  {7.11.0}  0°  25'  and  for  {580}  0°  35'. 
Although  the  difference  is  shghtly  less  for  the  more  complex  symbol, 
the  agreement  is  far  from  satisfactory.  The  correct  symbol  of  the 
form  is  therefore  in  doubt,  and,  though  the  indices  would  seem  to 
be  possibly  simpler  than  {7.11.0},  these  indices  are  inserted  in  the 
table  of  forms,  but  are  marked  with  a  (?)  to  indicate  that  the  sym- 
bols need  verification.     (See  also  p.  55.) 

w{021}  was  noted  only  by  Descloizeaux  and  by  Jeremejew. 
Attention  is  called  to  the  fact  that  {021}  occupies  almost  exactly 
the  same  position  as  c{001}  in  twin  position.  It  is  therefore  possible 
that  a  face  of  c{001}  in  twin  position  (as  shown  in  fig.  35)  was 
measured  and  taken  for  (021). 

c(OOl)  :  m;(021)=60°  OV  (calculated). 
c(OOl)  :  e(001)=60°  02'  (calculated;  p.  62 

The  difference  between  the  two  values  is  so  small  as  to  be  unmeasur- 
able.  It  seems  right,  therefore,  to  regard  the  form  w{02l)  as  doubt- 
ful and  as  at  least  needing  verification  before  it  can  be  accepted  as 
a  definite  form. 


70 


COLORADO   FERBEKITE   AND   THE   WOLFRAMITE   SERIES. 


^{095},  found  only  by  Descloizeaux,  also  needs  verification.  The 
measured  angle  agrees  much  better  with  the  slightly  more  complex 
form  {0.11.6}. 

(Oil)  :  (095)     =16°  47^  (measured  by  Descloizeaux). 
(Oil)  :  (095)     =16°  26^  (calculated);  difference  =+2K 
(Oil)  :  (0.11.6)=16°  64'  (calculated);  difference  =-07^ 

The  form  is  therefore  considered  doubtful,  on  account  of  the  im- 
certainty  of  its  symbol  and  because  it  needs  verification. 


\ 

www  1 

III  1111/ 

/' 

\ 

4 

k 

i      / 

/ 
/ 

h 

b  - 

£ 

\r   , 

V         / 

r.^'    \ 

/^'  J^     \ 

^vN 

r^.> 

w^^ 

/ 

Tv^X 

\    .^   -^ 

R^ 

^/ 

^7V 

&>          \ 

y 

''"/ 

H 

\         ^ 

\ 
\ 

1    ^ 

K 

/ 

/     //////  i . 

mm.    \ 

\ 

Figure  35. — Gnomonic  projection  of  forms  of  the  wolframite  group.  Several  forms  are  plotted  in  twin 
X)osition  (open  circle)  to  show  their  close  position  to  untwinned  forms.  Thus  note  particularly  c  and  w, 
i  and  t,  i[  and  a,  t  and  s,  s  and  «,  4  and  V. 

^{304},  described  only  by  Groth  and  Arzruni,  is  also  doubtful,  as 
the  measured  angles  vary  considerably  from  the  values  calculated 

for  them. 

Angles  for  the  form  ^{304}. 


Angle. 

Measured. 

Calculated. 

Difference. 

(001)  :(S04) 

(102)  :(304) 

(304):  (101) 

39    56 
11    51 
9    17 

38    23 
10    30 
8     15 

+  1    33 
+  1    15 

+  1    02 

FORM   SYSTEM  OP   THE  WOLFRAMITE   GROUP.  71 

>1{T01},  described  first  by  Groth  and  Arzruni  and  later  noted  by 
Groth  (but  without  measurement),  is  also  doubtful.  (001)  :  (TOl)  — 
48°  37'  measured  and  46°  38'  calculated,  the  difference  being  1°  59'. 

z{113}  given  by  Miller  ^  has  always  been  considered  a  questionable 
form.  Though  inserted  by  Goldschmidt  in  his  Winkeltabellen  with 
a  query,  it  had  best  be  omitted.  The  symbol  may  be  a  misprint 
for  {112}. 

Eakle  gives  the  letter  v  to  a  new  form  {T22}  on  wolframite  from 
Nevada,  but  as  the  letter  v  is  already  preempted  by  the  form  {552}, 
Eakle's  letter  is  changed  to  V.  Eakle's  letter  li  should  be  changed 
to  d  and  d  changed  to  e. 

It  may  be  noted,  too,  that  the  correctness  of  the  positive  or  nega- 
tive character  of  several  of  the  forms  listed  is  very  questionable. 
This  is  particularly  true  of  the  domes  described  by  Krenner,  who 
himself  called  attention  to  this  uncertainty. 

Figure  35  shows  the  gnomonic  projection  of  all  the  known  forms  of 
the  wolframite  series  except  t{321},  which  falls  outside  of  the  projec- 
tion, and  x{754},  which  was  described  after  the  gnomonic  projection 
was  drawn  and  reproduced.  The  position  of  the  forms  is  indicated 
in  figure  35  by  dots,  whereas  the  position  of  some  of  the  forms  in  twin 
position  (twinned  on  {023})  is  shown  by  open  circles. 

All  the  forms  lie  in  well-developed  zones.  The  prism  zone  is  the 
richest,  containing  a  total  of  17  forms,  but  hardly  any  of  the  simple 
zones  are  poor  in  forms. 

The  position  of  many  of  the  twinned  forms  is  nearly  identical  with 
other  forms  which  are  not  twinned  and  which  are  in  their  normal 
position,  as,  for  example,  ^{T02}  and  g{121},  c{001}  and  w{02l}, 
i{102}  and  s{T21},  .9{T21}  and  ^{102},  ^{121}  and  y{T02},  fi{l21} 
and5{T21}. 

FORMS   AND    COORDINATE   ANGLES. 

The  following  table  of  forms  and  coordinate  angles  shows  several 
points  to  which  attention  may  be  called.  If  a  form  is  considered 
doubtful — that  is,  if  it  seems  uncertain  whether  such  a  form  actually 
exists — the  question  mark  used  to  indicate  this  is  placed  with  and 
immediately  following  the  letter  of  the  form.  Thus  w  ?{021 }  means 
that  there  is  doubt  as  to  whether  such  a  form  has  actually  been  found. 
If,  on  the  other  hand,  there  is  no  question  about  the  existence  of  the 
form,  but  the  symbols  seem  to  be  incorrectly  determined,  or  at  least 
a  verification  of  the  correctness  of  the  measurement  is  desired,  the 
question  m-ark  is  placed  after  the  symbols,  thus  /S'{7.11.0}  ?. 

References  are  given  when  the  form  has  been  seen  and  described 
by  only  one  observer  or  two  independent  observers.  If  at  least  three 
different  observers  have  noted  the  form  its  confirmation  would  seem 

1  Miller,  W.  H.,  Elementary  introduction  to  mineralogy,  p.  473, 1852. 


72 


COLORADO   FEBBEEITE   AND   THE   WOLFRAMITE   SERIES. 


to  be  SO  well  established  that  references  to  it  are  in  general  not  neces- 
sary. The  occurrence  of  the  form  on  the  three  members  of  the 
wolframite  group  has  also  been  noted. 

Forms  and  coordinate  angles,  wolframite  grou^. 

[a=0.8255;  c-0.8664;  /9=89'' 32'.] 


No. 


37 


Letter. 


c 
b 
a 
r 

8 

m 
I 

R 
C 
F 

Q 
d 
G 

M 

N 

i 

n 
wt 

gf 

f 
r 
tt 
? 
y 

t 

df 

kf 

h 

i 

H 

k 
C 
V 
s 


Symbol. 

Gold- 
schmidt. 

Miller. 

0 

001 

Ooo 

010 

oo  0 

100 

oo2 

120 

oo  -V- 

7.11.0? 

oo 

110 

2oo 

210 

-V-  oo 

15. 7. 0 

ioo 

940 

|oo 

520 

IS 

830 

310 

Joo 

720 

500 

510 

V03 

11.2.0 

6oo 

610 

Too 

710 

SCO 

810 

02 

021 

Of 

095 

01 

Oil 

-tVO 

LO.ll 

+    0 

104 

+J0 

-io 

103 

102 

+  iO 

102 

-jo 

304 

-10 

101 

+  10 

101 

-JO 

403 

+1 

904 

-f  0 

602 

132 

— i  1 

122 

-12 

121 

+  12 

121 

+H 

123 

+A  T*l 

5.9.14 

+  H 

313 

-i 

112 

-1 

111 

-f 

S52 

+  1 

111 

+  i 

112 

+f 

337 

+51 

754 

-i? 

i?l 

+H 

214 

90  00 
0  00 
90  00 
31  12 
37  38 

50  27 

67  34 

68  58 

69  51 

71  44 

72  48 
74  37 
76  44 

80  38 

81  28 

82  10 

83  16 

84  06 
0  16 
0  18 

0  32 
90  00 
90  00 
90  00 
90  00 

90  00 
90  00 
90  00 
90  00 
90  00 

90  00 
90  00 
21  41 

30  48 

31  00 

31  24 
31  47 
34  31 
47  21 
50  01 

50  14 
50  22 
50  40 
50  53 

50  58 

59  35 
61  14 
67  29 
67  53 


0  28 
90  00 
90  00 
90  00 
90  00 

90  00 
90  00 
90  00 
90  00 
90  00 

90  00 
90  00 
90  00 
90  00 
90  00 

90  00 
90  00 
90  00 
60  00 
57  20 

40  54 
4  59 
15  08 
19  41 

27  19 

28  03 
37  55 
46  10 
46  36 
54  17 

67  07 
69  04 
54  26 
45  15 
63  41 

63  46 
34  12 
34  03 
74  44 

33  59 

53  34 

73  35 
53  49 

34  29 
30  31 

64  57 

74  29 
66  10 

29  55 


Refer- 


12 

13 

4,13 

2,3 

2 


4,13 

3,13 

3 


Ferberite, 
FeWOi. 


4 
4,6 
5,6 


7 

ii'is 


Wolframite, 

(Fe,Mn) 

WO.. 


Hiibnerite, 
MnWOi. 


a  Numbers  refer  to  the  Bibliography,  pp.  74-75. 


COLORADO   FERBERITE   AND  THE   WOLFRAMITE   SERIES. 


73 


COMBINATIONS   OBSERVED   ON   THE   WOLFRAMITE    GROUP. 

The  following  table  shows  the  combinations  described  on  minerals 
of  the  wolframite  gi-oiip  commencing  with  the  definite  sstablishmcnt 
of  the  monoclinic  character  of  the  group  by  Descloizeaux  in  1 850. 
As  wolframite  was  considered  to  be  orthorhombic  in  the  earlier 
debcriptions,  the  combinations  of  those  writers  are  not  given,  as  the 
positive  and  negative  forms  can  not  be  differentiated.  Numbers 
after  names  of  authors  refer  to  similar  numbers  in  the  bibliography. 

Combination  No.  10  gives  the  entire  list  of  forms  mentioned  by 
Descloizeaux  and  doubtless  represents  several  crystals,  in  part  prob- 
ably the  same  as  combinations  Nos.  1,  2,  and  3.  Combination  11 
hkewise  gives  the  complete  list  of  forms  observed  by  Jeremejew,  as 
I  was  not  able  to  decipher  the  individual  combinations  from  the 
Russian  text. 

CoTnbinations  described  on  crystals  of  minerals  of  the  woljramite  group. 


No. 


Combination. 


bamlfoo) 

amlfoo) 

amlfgyt 

cbamlfyt 

c  o  7n  l/s  0(0 

amlfyts 

amlfytso 

arml/yts 

bamtot 

cbarmlwgfytSffOd). 
cbarmlwfuqytSffOt 
cbamriTryirXtot 


bak ; 

baik 

badik 

cbd 

bat 

bayh 

bay 

bhv 

baiv 

cbadyik^e 

cafho 

amlXhffo) 

bam 

cbamlfyaoeoazi 

amfy 

b(ajmdftcj 

b(a)mQt 

b(a)mQtJ 

amlft 

amfo 

cbaSmlfytJ 


camlfytsirOeo. 
cb{a)mltj  p... 


cbamdj/yteooiJ. 

cbaml/tow 

cbarmadstoe  V. 
cbamlatx 


Mineral. 


Wolframite. 

do 

do 

do 


.do. 
.do. 
.do. 
.do. 

.do. 
.do. 


.do. 


....do.. 
....do.. 
....do.. 


Iliibnerite., 
Wolframite. 

do 

Hubnerite.. 
....do 


do 

Wolframite. 

do 

Ferberite... 

Wolframite. 
Ferberite... 


....do 

Wolframite. 

do.o... 

HUbnerite. . 


Locality. 


Chanteloube. 

do 

do 

Altenberg 

do 


Zinnwald 

do 

do 

Schlaggenwald . 
Chanteloube... 
Altai,  Russia... 
Schlaggenwald. 


Felsobanya. 
do 


.do. 


....do. 
....do. 
....do. 


do.... 

Altenberg. 
Zinnwald. 


Spain 

Fiehtelgebirge 

Silverton,Colo... 

New  Mexico , 

do 


Altai 

Japan 

South        Dakota 

(Colorado?). 
New  South  Wales. 
Boulder    County, 

Colo. 

Greenland 

Bolivia 

Nevada 

Peru 


Author. 


Descloizeaax  (1). 

...-do.(l) 

-..-do.(l) 


.do.(l). 
.do.(l). 
.do.(I), 
.do.(l). 


do.(l) 

do. (2) 

do. (2) 

Jeremejew  (3) 

Groth   and    Arz- 
runi  (4). 

Krenner  (5) , 

do.(5) 

do.(5) 

do.(5) 

do.(5) 

do.(5) , 

do.(5) 

do.(5) 

do.(5) 

do.(5) 

Groth(6) 

do.(6) 

Bertrand  (7) 

Seligman(8) 

Sandbergcr  (9) 

Penfleld(lO) 

do.  (10) 

do.(lO) 

Jeremejew  ( 11 )... . 

Jimbo(12) 

Warren  (13) 


Anderson  (14). 
Moses  (15) 


B6ggild(l«)... 
Spencrer(17)..- 

Eakle(18) 

Tronquoy(19)- 


Date. 


1850 
1850 
1850 
1850 
1£50 
1850 
1850 
1850 
1870 
1870 
1872 
1873 

1875 
1875 
1875 
1875 
1875 
1875 
1875 
1875 
1875 
1875 
1878 
1878 
1882 
1880 
1888 
1892 
1892 
1892 


1901 

1904 
1905 

1905 
1907 
1912 
1913 


o  Eaklo  states  that  "All  of  the  material  contains  iron  and  is  to  be  classed  as  wolframite  rather  than  as 
hubnerite."  His  next  sentence, "  The  crystals  aro  tabular  parallel  to  tho  orthopinacoid  and  some  of  them 
are  exceedingly  thin  and  almost  transparent,  wiih  a  deep-red  color,"  would  indicate,  however,  that  the 
material  was  more  likely  hubnerite  than  wolframite. 


74  COLORADO   FERBERITE   AND   THE    WOLFRAMITE   SERIES. 

The  following  combinations  were  observed  by  the  writer  on  the 
ferberite  from  Colorado  described  in  this  report: 

cbamlf  cbamlfrioeo  chamlf 

cbamlf  cbamlfo  cbaml 

cbamlf  (u  cbamldjf  trwo  cbamlf 

cbamlp  cbamlMnfut  IIBcuJA  cbamlRQnft 

cbamlp  cbamlGMNLntHAso  cbatllE 

cbamlRCHto  cbamlftllwJA  cbatH 

cbamlf  o)  cbamlt  IIwJ  cbatj 

cbamlf (upo  cbaml  Nnftjo  cbat 

cbamlf  H(ao  cbamlR  CQtj  cbaltj 

cbamlfrcao  cbamlf  t  HB  Em  JpD  baUH 

cbamlr  CFMf  cbamlftHwJA  baltH 

cbamlf  cbamlft  EAA  cbatH 

cbamlLnf  cbaml  Fftwd 

By  calculatiQg  the  percentage  occurrence  for  the  77  combuiations 
listed  (the  39  given  in  the  table  and  the  38  observed  by  the  writer), 
the  forms  of  the  wolframite  group  fall  into  three  classes,  as  follows : 

(1)  Prominent  forms: 

Letter a  h  m  c  I  ft 

Symbol (100)     (010)     (110)     (001)     (210)     (Oil)     (102) 

Per  cent  of  occurrence 97         84         75         67         67         57         51 

(2)  Less  prominent  forms: 

Letter co  o  d  y  H  s  o 

Symbol (Ill)     (111)     (112)     (T02)     (904)     (121)     (121) 

Per  cent  of  occurrence 35         24         21         21         17         12         11 

(3)  Rare  forms:  AH  the  remaining  forms,  35  in  immber. 

BIBLIOGRAPHY. 

1.  Descloizeaux,  A.,  Memoire  sur  les  formes  cristallines  du  wolfram:  Annales  chim. 

et  phys.,  3d  ser.,  vol.  28,  p.  163,  1850. 

2.  Descloizeaux,  A.,  Nouvelles  recherches  cristallographiques   et  optiques  sur  la 

forme  clinorhombique  du  wolfram:  Annales  chim.  et  phys.,  4tli  ser.,  vol.  19, 
p.  168,  1870. 

3.  Jerfemejew,  P.,  Wolfram- Krystalle  im  Vergleich  zu  den  Krystallen  des  Columbite: 

Russ.-k.  mineral.  Gesell.  St.  Petersburg  Verb.,  2d  ser.,  vol.  7,  p.  301,  1872. 

4.  Groth,  P.,  and  Arzruni,  A.,  Ueber  die  Krystallform  und  die  optische  Eigenschaften 

des  Wolframs  und  dessen  Beziehungen  zum  Columbit:  Poggendorff's  Annalen, 
5th  ser.,  vol.  29,  p.  235,  1873. 

5.  Krenner,  J.  A.,  Wolframit  aus  dem  Trachyte  von  Felso-Banya:  Min.  pet.  Mitt., 

vol.  5,  p.  9,  1875. 

6.  Groth,  P.,  Die  Mineraliensammlung  der  Kaiser- Wllhelms-Universitat,  Strassburg, 

p.  161,  1878. 

7.  Bertrand,  E.,  Sur  la  hubn^rite  des  Pyr^n^es:  Soc.  min.  de  France  Bull.  5,  p.  90, 

1882. 

8.  Seligmann,  G.,MineralogischeNotizen,  III;  12,  Wolframit:  Zeitschr.  Kryst.Min., 

vol.  11,  p.  347,  1886. 

9.  Sandberger,  F.,  Ueber  Lithionitgranite  mit  besonderer  Rucksicht  auf  jene  des 

Fichtelgebirges,  Erzgebirges  und  des  nordlichen  Bohmens:  K.  bayer.  Acad. 
Miinchen,  Math. -phys.  Classe,  Sitzungsber.,  1888,  p.  423. 
10.  Penfield,  S.  L.  (with  Genth,  F.  A.),  Mineral  notes,  No.  52:   Am.  Jour.  Sci.,  3d 
ser.,  vol.  43,  p.  184,  1892. 


BIBLIOGRAPHY.  75 

11.  JeremeJGw,  P.,  Ueber  den  Wolf  rami  t  von  der  Demidow'schen  Kupfergrube  in 

der  Niihe  dos  Kolywan'schen  Bergwerkes,  Altai:  Russ.-k.  mineral.  Geaell. 
Verb.,  vol.  31,  p.  404,  1894. 

12.  Jimbo,  K.,  Notizen  (iber  die  Mineralien  von  Japan:  Tokyo  Coll.  Sci.  Jour.,  vol. 

11,  p.  213,  1899. 

13.  Warren,  C.  H.,  Mineralogical  notes:  Crystal  of  iron  wolframite  from  South  Dakota: 

Am.  Jour.  Sci.,  4th  sor.,  vol.  11,  p.  372,  1901. 

14.  Anderson,  C,  Mineralogical  notes  No.  I:  Topaz,  beryl,  vesuvianite,  tourmaline, 

and  wolframite:  Australian  Mus.  Records,  vol.  5,  p.  303,  1904. 

15.  Moses,  A.  J.,  The  crystallization  of  luzonite  and  other  crystallographic  studies; 

Crystallized  wolframite  from  Boulder  County,  Colo.:  Am.  Jour.  Sci.,  4th  ser., 
vol.  20,  p.  281,  1905. 

16.  Boggild,  O.  B.,  Mineralogia  Groenlandica:  Meddelelser  om  Greenland,  No.  32, 

p.  179,  1905. 

17.  Spencer,  L.  J.,  Minerals  from  Bolivia:  Mineralog.  Mag.,  vol.  14,  p.  334,  1905. 

18.  Eakle,  A.  S.,  The  minerals  of  Tonopah,  Nev.:  California  Univ.  Dept.  Geology 

Bull.,  vol.  7,  p.  18,  1912. 

19.  Tronquoy,  R.,  Surla  hubn^rite:  Soc.  fran?.  min^ralogieBull.  36,  p.  113, 1913. 

O 


